Is there an option in your computer's BIOS to turn NumLock off? (Edit: My bad... Didn't realize you edited your post... Let me think of something else.) Not sure if this will work, but set that value to 0, restart your machine, and set NumLock to ON in your BIOS right before it boots into the OS (NumLock's a toggle switch, so there's a possibility that the BIOS and OS may be conflicting with each other - i.e., when it's off in the BIOS, W7 may want to turn it on and vice versa).