diff --git a/src/main/scala/li/cil/oc/CreativeTab.scala b/src/main/scala/li/cil/oc/CreativeTab.scala
index d76309da8..75a2af441 100644
--- a/src/main/scala/li/cil/oc/CreativeTab.scala
+++ b/src/main/scala/li/cil/oc/CreativeTab.scala
@@ -2,18 +2,11 @@ package li.cil.oc
 
 import cpw.mods.fml.relauncher.Side
 import cpw.mods.fml.relauncher.SideOnly
-import li.cil.oc.common.Loot
 import net.minecraft.creativetab.CreativeTabs
 
 object CreativeTab extends CreativeTabs(CreativeTabs.getNextID, "OpenComputers") {
   @SideOnly(Side.CLIENT)
   override def getTabIconItemIndex = Settings.get.blockId2
 
-  override def displayAllReleventItems(list: java.util.List[_]) = {
-    def add[T](list: java.util.List[T], value: Any) = list.add(value.asInstanceOf[T])
-    super.displayAllReleventItems(list)
-    Loot.disks.foreach(add(list, _))
-  }
-
   override def getTranslatedTabLabel = getTabLabel
 }
\ No newline at end of file
diff --git a/src/main/scala/li/cil/oc/Items.scala b/src/main/scala/li/cil/oc/Items.scala
index 4fff8f2f9..ef5cc6025 100644
--- a/src/main/scala/li/cil/oc/Items.scala
+++ b/src/main/scala/li/cil/oc/Items.scala
@@ -1,13 +1,15 @@
 package li.cil.oc
 
 import cpw.mods.fml.common.registry.GameRegistry
-import li.cil.oc.common.item
+import li.cil.oc.common.{Loot, item}
 import li.cil.oc.util.mods.Mods
 import net.minecraft.item.{Item, ItemBlock, ItemStack}
 import scala.collection.mutable
 import li.cil.oc.api.detail.{ItemAPI, ItemInfo}
 import net.minecraft.block.Block
 import li.cil.oc.common.recipe.Recipes
+import net.minecraft.nbt.NBTTagCompound
+import net.minecraft.creativetab.CreativeTabs
 
 object Items extends ItemAPI {
   private val descriptors = mutable.Map.empty[String, ItemInfo]
@@ -69,7 +71,8 @@ object Items extends ItemAPI {
     instance
   }
 
-  private def getBlockOrItem(stack: ItemStack): Any = if (stack == null) null else {
+  private def getBlockOrItem(stack: ItemStack): Any = if (stack == null) null
+  else {
     multi.subItem(stack).getOrElse(
       Blocks.blockSimple.subBlock(stack).getOrElse(
         Blocks.blockSimpleWithRedstone.subBlock(stack).getOrElse(
@@ -93,7 +96,14 @@ object Items extends ItemAPI {
   var ironNugget: item.IronNugget = _
 
   def init() {
-    multi = new item.Delegator(Settings.get.itemId)
+    multi = new item.Delegator(Settings.get.itemId) {
+      override def getSubItems(itemId: Int, tab: CreativeTabs, list: java.util.List[_]) {
+        // Workaround for MC's untyped lists...
+        def add[T](list: java.util.List[T], value: Any) = list.add(value.asInstanceOf[T])
+        super.getSubItems(itemId, tab, list)
+        Loot.worldDisks.values.foreach(entry => add(list, entry._1))
+      }
+    }
 
     GameRegistry.registerItem(multi, Settings.namespace + "item")
 
@@ -184,5 +194,23 @@ object Items extends ItemAPI {
     Recipes.addItem(new item.UpgradeContainerCard(multi, 0), "cardContainer1", "oc:cardContainer1")
     Recipes.addItem(new item.UpgradeContainerCard(multi, 1), "cardContainer2", "oc:cardContainer2")
     Recipes.addItem(new item.UpgradeContainerCard(multi, 2), "cardContainer3", "oc:cardContainer3")
+
+    // Special case loot disk because this one's craftable and having it have
+    // the same item damage would confuse NEI and the item costs computation.
+    Recipes.addItem(new item.FloppyDisk(multi) {
+      override def createItemStack(amount: Int) = {
+        val data = new NBTTagCompound()
+        data.setString(Settings.namespace + "fs.label", "openos")
+
+        val nbt = new NBTTagCompound("tag")
+        nbt.setTag(Settings.namespace + "data", data)
+        nbt.setString(Settings.namespace + "lootPath", "OpenOS")
+
+        val stack = super.createItemStack(amount)
+        stack.setTagCompound(nbt)
+
+        stack
+      }
+    }, "openOS")
   }
 }
\ No newline at end of file
diff --git a/src/main/scala/li/cil/oc/common/Loot.scala b/src/main/scala/li/cil/oc/common/Loot.scala
index 39ba2e6a9..04b6f5529 100644
--- a/src/main/scala/li/cil/oc/common/Loot.scala
+++ b/src/main/scala/li/cil/oc/common/Loot.scala
@@ -1,6 +1,6 @@
 package li.cil.oc.common
 
-import net.minecraftforge.common.ChestGenHooks
+import net.minecraftforge.common.{DimensionManager, ChestGenHooks}
 import net.minecraft.util.WeightedRandomChestContent
 import net.minecraft.nbt.NBTTagCompound
 import scala.collection.convert.WrapAsScala._
@@ -8,8 +8,11 @@ import java.util.Random
 import net.minecraft.inventory.IInventory
 import net.minecraft.item.ItemStack
 import scala.collection.mutable
-import li.cil.oc.{Settings, api}
+import li.cil.oc.{OpenComputers, Settings, api}
 import li.cil.oc.common.recipe.Recipes
+import java.io
+import net.minecraftforge.event.ForgeSubscribe
+import net.minecraftforge.event.world.WorldEvent
 
 object Loot extends WeightedRandomChestContent(api.Items.get("lootDisk").createItemStack(1), 1, 1, Settings.get.lootProbability) {
   val containers = Array(
@@ -18,6 +21,10 @@ object Loot extends WeightedRandomChestContent(api.Items.get("lootDisk").createI
     ChestGenHooks.PYRAMID_JUNGLE_CHEST,
     ChestGenHooks.STRONGHOLD_LIBRARY)
 
+  val builtInDisks = mutable.Map.empty[String, (ItemStack, Int)]
+
+  val worldDisks = mutable.Map.empty[String, (ItemStack, Int)]
+
   val disks = mutable.ArrayBuffer.empty[ItemStack]
 
   def init() {
@@ -26,16 +33,64 @@ object Loot extends WeightedRandomChestContent(api.Items.get("lootDisk").createI
     }
 
     val list = new java.util.Properties()
-    val listFile = getClass.getResourceAsStream("/assets/" + Settings.resourceDomain + "/loot/loot.properties")
-    list.load(listFile)
-    listFile.close()
+    val listStream = getClass.getResourceAsStream("/assets/" + Settings.resourceDomain + "/loot/loot.properties")
+    list.load(listStream)
+    listStream.close()
+    parseLootDisks(list, builtInDisks)
 
-    for (key <- list.stringPropertyNames) {
-      disks += createLootDisk(key, list.getProperty(key))
+    for ((name, (stack, _)) <- builtInDisks if name == "OpenOS") {
+      Recipes.list += stack -> "openOS"
     }
   }
 
-  def createLootDisk(name: String, path: String) = {
+  @ForgeSubscribe
+  def initForWorld(e: WorldEvent.Load) {
+    worldDisks.clear()
+    disks.clear()
+    val path = new io.File(DimensionManager.getCurrentSaveRootDirectory, Settings.savePath + "loot/")
+    if (path.exists && path.isDirectory) {
+      val listFile = new io.File(path, "loot.properties")
+      if (listFile.exists && listFile.isFile) {
+        try {
+          val listStream = new io.FileInputStream(listFile)
+          val list = new java.util.Properties()
+          list.load(listStream)
+          listStream.close()
+          parseLootDisks(list, worldDisks)
+        }
+        catch {
+          case t: Throwable => OpenComputers.log.warning("Failed opening loot descriptor file in saves folder.")
+        }
+      }
+    }
+    for ((name, entry) <- builtInDisks if !worldDisks.contains(name)) {
+      worldDisks += name -> entry
+    }
+    for ((_, (stack, count)) <- worldDisks) {
+      for (i <- 0 until count) {
+        disks += stack
+      }
+    }
+  }
+
+  private def parseLootDisks(list: java.util.Properties, acc: mutable.Map[String, (ItemStack, Int)]) {
+    for (key <- list.stringPropertyNames if key != "OpenOS") {
+      val value = list.getProperty(key)
+      val splitAt = value.lastIndexOf(':')
+      if (splitAt >= 0) {
+        val (name, count) = value.splitAt(splitAt)
+        try {
+          acc += key -> (createLootDisk(name, key), count.toInt)
+        }
+        catch {
+          case _: Throwable => OpenComputers.log.warning("Bad loot descriptor: " + value)
+        }
+      }
+      else acc += key -> (createLootDisk(value, key), 1)
+    }
+  }
+
+  private def createLootDisk(name: String, path: String) = {
     val data = new NBTTagCompound()
     data.setString(Settings.namespace + "fs.label", name)
 
@@ -47,10 +102,6 @@ object Loot extends WeightedRandomChestContent(api.Items.get("lootDisk").createI
     val disk = api.Items.get("lootDisk").createItemStack(1)
     disk.setTagCompound(tag)
 
-    if (name == "OpenOS") {
-      Recipes.list += disk -> "openOS"
-    }
-
     disk
   }
 
diff --git a/src/main/scala/li/cil/oc/common/Proxy.scala b/src/main/scala/li/cil/oc/common/Proxy.scala
index 8520e705f..78e5f4555 100644
--- a/src/main/scala/li/cil/oc/common/Proxy.scala
+++ b/src/main/scala/li/cil/oc/common/Proxy.scala
@@ -92,15 +92,16 @@ class Proxy {
     api.Driver.add(driver.converter.FluidTankInfo)
     api.Driver.add(driver.converter.ItemStack)
 
+    Loot.init()
+    Recipes.init()
+    GameRegistry.registerCraftingHandler(CraftingHandler)
+
     MinecraftForge.EVENT_BUS.register(RobotCommonHandler)
     MinecraftForge.EVENT_BUS.register(ExperienceUpgradeHandler)
     if (Mods.UniversalElectricity.isAvailable) {
       MinecraftForge.EVENT_BUS.register(UniversalElectricityToolHandler)
     }
-
-    Loot.init()
-    Recipes.init()
-    GameRegistry.registerCraftingHandler(CraftingHandler)
+    MinecraftForge.EVENT_BUS.register(Loot)
 
     FMLInterModComms.sendMessage("Waila", "register", "li.cil.oc.util.mods.Waila.init")
   }
diff --git a/src/main/scala/li/cil/oc/common/tileentity/RobotAssembler.scala b/src/main/scala/li/cil/oc/common/tileentity/RobotAssembler.scala
index 03522cd11..5a3e9ce65 100644
--- a/src/main/scala/li/cil/oc/common/tileentity/RobotAssembler.scala
+++ b/src/main/scala/li/cil/oc/common/tileentity/RobotAssembler.scala
@@ -47,7 +47,10 @@ class RobotAssembler extends traits.Environment with traits.Inventory with trait
 
   def start() {
     if (!isAssembling && robot.isEmpty && complexity <= maxComplexity) {
-      // TODO validate all slots, just in case. never trust a client. never trust minecraft.
+      for (slot <- 0 until getSizeInventory) {
+        val stack = getStackInSlot(slot)
+        if (stack != null && !isItemValidForSlot(slot, stack)) return
+      }
       val data = new ItemUtils.RobotData()
       data.name = ItemUtils.RobotData.randomName
       data.energy = 50000