bumps

i there ;), when i'm playing, the image on my 17 crt monitor it kinda has some bumps. i mean, for exmaple, fraps tells me that i'm running Prey over 45 fps and has that bumps.what ca i do?? by the way i have an 2.8 dual core, xfx8600gt, 2 ram and xp! i apreciate some help and sorry about the...