Currently Being ModeratedApr 15, 2012 5:38 PM (in response to lynchrn)
Check System Preferences > Desktop & Screensaver.
There you will find option to change the desktop every so many minutes which you can deselect.
The screensaver can also be set to random..
Virus Nope. and the fix for the trojen which may have affected 1% of the Mac user base has already been available in software update.
Currently Being ModeratedApr 15, 2012 9:20 PM (in response to lynchrn)
I have been getting this crazy colored screen savers and backgrounds that I never set.
Doesn't sound like any malware I know. Based on that description, you're not infected. If, nevertheless, you feel you may be, provide more details.