keyboard freaking out unless i use Fn key

i don't know what happened, but my keyboard has changed to where certain keys don't type what they're labelled as (or don't show up at all) unless i press and hold down the Fn key while i type that key. What happened and how do i fix it? i'm using Windows XP. i checked the accessibility features and rooted around on the microsoft.com website ~ no luck.

To demonstrate the problem, i'll retype what i wrote above without going back and fixing the letters with the Fn key:

d6n't 2n6w what ha**ened, b4t 0y 2eyb6ard has changed t6 where certa5n 2eys d6n't ty*e what they're 3abe33ed as 6r d6n't sh6w 4* at a33 4n3ess *ress and h63d d6wn the Fn 2ey wh53e ty*e that 2ey. What ha**ened and h6w d6 f5s 5t+ '0 4s5ng w5nd6ws X*. chec2ed the access5b535ty feat4res and r66ted ar64nd 6n the 05cr6s6ft.c60 webs5te ~ n6 34c2.



Thanks y'all!!