The screen seems to vibrate, the cd burner has a failure every time I try to burn a back up cd for my files, and a few times I recieved a message stating that Windows XP did not start up properly.  One time when the computer was running poorly it also stated that the virtual memory was full even though no programs were running.  The compuer is now taking longer and longer to boot up now.  Also the screen PIXEL size changed and the display shrunk from 1152 x 864 to 1024 x 768 and also the monitor didn't allow me to change the screen setting with the OSD buttons on the monitor.  This all started on the same day and am not sure if it is related.  I set the systems restore back a week to see if that would help.  It changed the pixel size back to normal but all the other problems persist.  If anyone knows what I can do to fix the problem I would love any advice.Have you tried all the usuals like scandisk, defragment, virus checkers? Another anwser maybe that the hard drive as given up. Sounds like you have quite a few problems, is it an old computer?OSUdental....As I read your post it seems that all these problems started at the same time......If thats correct ,them possibly the issue is with your video card.
The other possibility is a virus or trojan......Have you scanned for them with current and updated scanning software .
Anything else about whats going on might help find a solution for you.

dl65    I have recently scandissked the computer and that doesn't seem to be the problem, I also ran disk defragmenter about a week and a half before this problem.  I have bought a new video card but haven't installed it since I was worried that it may be useless if I have to buy a new computer.  This one is 2 yrs old, is an entry level E-machines, so it is not top of the line I KNOW, but still I don't understand the problem.  Any suggestions on a good virus software?  Don't have a LOT of money, but it would be a lot cheaper than a new comp.

(As a side note I'm not sure my new video card will fit into the slot on the motherboard.  Is that common and can it be corrected?)e-machines ok?virus software and FIREWALLS etc can be found here>http://www.majorgeeks.com/download955.html   the pc acting weird possible trojan?SCAN with the stinger progamOSUdental...You didn't mention whether you are running
a anti virus program.......Be sure it's updates are current.
Perhaps you should download and scan with Ad-Aware
http://www.lavasoftusa.com/    it's free and is very good.
With regard to your vid card question ........I thinks there's at least 3  types of slots.
ISA    older style
PCI    in most p/c's
AGP   newest of the lot I think.
So if your going to upgrade your vid card .....the first thing you should do is learn the difference between the slot types. It is possible your p/c has an onboard vid card. If that is the case you would install the new one in a vacant slot , install the new drivers and disable the onboard vid card. Then if you buy a new puter down the road , simply remove the one you just bought and enable the onboard vid card. Running scan disk and defragging isnt going to correect your problem , but it should improve the performance of your p/c . Run a complete in depth virus scan and then run the Ad-aware
program .You will be amased at how many things it will locate and remove.

good luck

dl65