Weird Graphics Problem

[dandubi]

I am having this problem with my graphic display on most of my games. my cousin has
the same set up same graphics card, same os but has 256 less ram mb then me. we both have the same drivers and version 9.0b of direct x.

my specs:
OS Windows XP Home
Pent 4 2.21 Ghz
512 Mb ram
Nvidia Geforce 4 MX 420

the game displays white lines flashing on screen.

http://www.angeltowns.com/members/dandubi/graphic.jpg
(Copy and paste Link)

u can see a screenshot of what i see here.
please if anyone knows what else i need to update it will help greatly thks

[Buzioid]

are you overclocking your card by any chance?
overclocking causes this a lot.

[Xtreeme]

Overclocking or heat.