Screen

[CWHarrisII]

I have an older Mac laptop. All of a sudden while working on it the screen will turn to orange/yellow stripes. I have to press the button to turn it off. When I turn it back on the screen is purple/black. If I turn it off again and let it sit for a while it will operate normally when turned back on. What's the problem?? How can I fix it???

 

[Giaguara]

What Mac?
What version of Mac OS X?
Does it seem to be related to the usage (when more processor or RAM in use), to temperature etc?
If you have the install discs that came iwth the computer, and you run Apple Hardware Test form them (it is listed on the appropriate disc), in looped mode (ctrl+L) for a few rounds, is any error reported?
Is there any added or user replaced RAM?