Screen flashing white

hi everyone

hopefully you guys can help me something. i know you'll want some details about my laptop so:

Windows 7 64 bit (SP1)

Dell Inspiron 1764 laptop

Intel Core i5 2.27 GHz

              Motherboard Chipset: Dell 0TKV96

              4 GB memory 

Video Card Type: Intel(R) Graphics Media Accelerator HD

Computer Monitor: Generic PnP Monitor (17.1"vis)

Hard Drive 500 GB

Anti-virus Software is Norton 360

BIOS: A13 (latest one)

 my problem is, for no apparent reason, my screen goes white and starts flashing. there's the odd flash of grey in there, but mostly all you can see is white - whatever i was working on previously is not visible at all.

i have to switch the comp off to make it stop. it's geting more frequent so i was hoping you could help me with some suggestions?

i've already updated relevant drives and bios, my power cord is connected proplerly, and i keep the computer out of the sun.

thanks in advance guys