OK. Now I'm beginning to get the picture.
I do not think that it is your screen, or even your graphics card.
You said "it usually only happens when I am on the internet switching back and forth between sites." So, when you are switching from browser window to browser window.
I am assuming that you are running Internet Explorer. First off, I would recommend that you download and try either Firefox (
http://www.mozilla.org/) or Opera (
http://www.opera.com/) and see it either of them works better for you.
If you prefer to stay with Internet Exploiter, uhhhh, Explorer, try this. Click
Tools (up on the top bar),
Interent Options, Delete Cookies, OK, Delete Files, check the "
Delete all offline content" box,
OK, Clear History, Yes, OK.
How much RAM are you running? Windows XP won't run all that great with 128MB. 256MB is a whole lot better, and anything above that is wonderful.
Also, check your hard drive (using Advisor). Make sure that it isn't too full.
One more thing. After all of this, defrag your hard drive. Click
Start, All Programs, Accessories, System Tools, Disk Defragmenter. Choose your hard drive and let it analyze it. It will probably say that you need to defrag, so tell it to.
Let me know if any of this helps.