I had that happen to me two days ago with my USB keyboard. It kept changing all the keys and opening the "search for files and folders", minimizing my game, muting the sound, killed all my hotkeys for my media player. It ended up being an undetectable trojan packed in a .rar file located in C:\Documents and Settings\All Users\Application Data called "Tray Shim Bore Idle.rar" That has 2 .exe files in it, but I can't remember the name (I think one was called bleh 32.exe). There was also a Tray Shim Bore folder in my user account's Application Data folder. You have to have hidden/system files showing to find them. Deleting those (if you do have them) and running a registry cleaner should fix it. It is also posible they could be named something else. Good luck with it