Windows 7 - No Signal crash, Black screen

Hi

I really hope someone out there can help me with this issue that i am having with my computer whilst i am playing world of warcraft. I seem to be getting a black screen after a random period of time and then the no signal sign pops up. the problem seems to intermittent for the most part but recent seems to be crashing after 5 minutes. i have read the forums and tried out the suggested methods on them, ie update drivers, uninstall/reinstall graphic card but the problem still persists. i have downloaded speedfan to monitor gpu temperatures but that is not presenting me with enough proof that the card is at fault, at least not enough to justify the expense of a new card.

operating system: Windows 7 home premium 64-bit
system manufacturer : packard bell
system model : ixtreme m5722
processor : intel core 2 quad cpu q8300 @2.50GHz
memory : 6144mb ram
running direct x 11
video card : Nvdia geforce gt220

let me just say that i am hopeless with technical terminology and finding my way around a pc so please help me with my problem but also keep it simple. hopefully this issue can be resolved with me spending a fortune on a new graphics card etc.

A way to test the graphic card is to use the GPU test in OCCT
OCCT (OverClock Checking Tool) 3.0.0 download from Guru3D.com

downloaded it and testing now

thanks

had exact problem
rmove pc cover
lay on side
get can of air small paint bruch and a hoover
clean out clogged up graphic card fan its on underside of graphic card
really simple and im a builder