Random computer freezing/weird display when gaming

Hey all,

Recently ive been having a couple of issues with my mac; the thing is i havent used it in a few months.

anyway lately when i have been using my computer if i dont use it for a few minutes it will freeze, causing me to force it to shut down. and the other issue is kinda hard to explain but for some reason when i am gaming the picture has been acting up lately; i can see almost perfectly fine but there are vertical lines all over the screen - about 2cm long...the lines only seems to pop up on 3d imaging.

i have an iMac PPC G5 with 512mb ram

like i said i have not used this computer in a while

thanks in advance for the help

-Devin

 

Okay I'll try that out. Thanks