Monitor resolution

Recently, my desktop (windows xp, sp3) has been behaving strangely. The screen wil go black for a second or two when switching between programs or web pages, as if it is adjusting the resolution of the screen ad hoc. The resolution indicator flashes on as if to confirm this. Is there a setting that I may have inadvertently changed which could be causing this? Also, when I attempt to get online help via instant messenger, the machine says that this program is not present, even though it is installed and functional. This problem does not seem to have any major effect other than annoying my significant other, who, like myself doesn't like changes without an apparent cause. Any suggestions?

Thank you in advance,

Mosander

 

My thinking?
Reinstall driver for your graphic card.Get the latest version from ATI or nVIDIA site.
Firstly uninstall display driver from add& remove,restart comp,install the new one.

BTW,I think you have ATI GPU card.