I have Microsoft Windows XP Professional, 2002 version, SP2
76487-OEM-0067582-34890
I have an AMD Athlon(tm) Processor  1.30 GHz, 256MB RAM (I know, horrible, my company will not upgrade)
My "Display Adapter" is an NVIDIA RIVA TNT2 Model 64/Model 64 Pro.

When I left work last night I turned off my computer as usual.  I do not know if anyone turned it back on and used it after I left, no one is admitting to it if they did.  When I turned the computer on this morning, the resolution was down to 800x600 with 4-bit color quality.  I have no option to increase either of these settings.  Also, a baloon popped up in the lower right hand corner of the screen telling me that my color settings were at the lowest.  I clicked the balloon and I got a window asking if I wanted Windows to automatically fix the  color problem.  I said yes, and NOTHING changed.  I restarted the computer, still nothing.  I have not INSTALLED or removed any programs or hardware.  Can anyone help?
What does it look like in Device Manager? Are there any errors?

START>right click "my computer">properties>hardware tab>device manager

Do you SEE any yellow exclamation marks anywhere?

If not, you might try updating the display driver anyway?

Click on the "+" sign next to "display adapters", then right click on the item in the submenu, and then click "update" to see if Windows will update it......Thank you for replying!

There are no exclamation points in the device manager. 
I attempted to update my display adapter, but it stopped and I got this message:

"The wizard could not find a better match for your hardware than the software you currently have installed."What if you try to do system restore? As you have said, you don't know if someone had used your computer..

Or you could reinstall your videocard. In the device Manager, Right click on the Display Adapter icon then choose uninstall. Then restart Windows and it will ask again for the card's drivers..THANKS Jerry.
Forgive my ignorance, but what is system restore, and how do I do it?

Click Start > Accessories > System Tools > System Restore
Read this for full instructions:
http://www.microsoft.com/windowsxp/using/helpandsupport/learnmore/systemrestore.mspx

Good Luck!
Jerry, you are my hero for the day!

I WENT to system restore, but it didn't find anything.  So I uninstalled the NVIDIA RIVA "display adapter" and viola!  I'm back in the 21st century!  Thanks everyone for all of your help, I will definitely recommend you and I'll come back myself if I run into any more problems!

JessThat's good news!
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