i'm having some problems with this ps/2 foldable keyboard I bought for my computer (running windows xp). Some keys don't type the character they're supposed to, or some type two. Like for example, the key j types "jf" instead of just j, and the f key does the same thing. The key 3 types 7, and other things. This device is supposed to be plug and play... Any idea how to fix things?