7 Key gone rogue

Please update after replacing your keyboard!!
I'm having the same problem with Presario 2104US laptop.

Removed keyboard and touchpad and plugged in a USB mouse and keyboard.

Tried a clean install of XP after running Killdisk. But as soon as it is time to type a name or anything in starts the 7777777777.

I can hold down a differant key, for example, z and I get 7z7z7z7z7z.

So with no keyboard just mouse and I click the cursor in a box and away go the 777777.

Please let me know if a new keyboard helps. Or if others may have ideas please post.

Thanks,
Butch