Computer Screen Flickers, Taskbar Appears On Top Of Screen...

[baseballst4r]

I have a Dell Dimension 2400, with a Samsung SyncMaster 731B monitor and here's my problem.  Everytime I leave my computer for a few hours, I return to it and the taskbar has gone to the top of the screen, the screen flickers (sometimes grey, sometimes white, and sometimes black), and none of the programs work on it.  After a couple minutes the mouse cursor will move around the screen but is not able to click on anything.  This has been happening for a few months and everytime it happens the only way to fix it is for me to hold the power button down until the computer shuts down then start it back up (I know you should never do this but Ctrl+Alt+Delete doesn't work and I cant get to the start button).  Once everything gets restarted it is fine, but when I leave it be for a few hours it happens all over again.


Here is a video I took of what my computer looks like when i return to it:

http://www.youtube.com/watch?v=lqf1d0Jy7Kk

Does anyone know what is possibly causing this and how to solve it? 

[Broni]

What Windows version, what browser?
You may have some infection.

[baseballst4r]

I have Windows XP home edition, and it is Internet Explorer 7.
I only said that internet explorer wouldn't open as an example, but any program that I try to open has the same result.

[Broni]

I think, you have to...
Start here:
http://www.computerhope.com/forum/index.php/topic,46313.0.html
Post all logs at Computer Viruses and Spyware forum.