Cannot Right Click On The Desktop

I can not Right Click on the Desktop of my PC. If I try to Right Click, all of the icons and the bottom toolbar dissapears for a second. The background is the only thing visible. And then it comes back after a second or two. Once ina while I get an error message but I cannot Right CLick to open a new folder or anything. It just turns blank. Here is what the error message said. Windows Explorer has encountered a problem and needs to close. and here are some of the details:

Error Signature
AppName: explorer.exe
AppVer 6.0.2800.1106
ModName msvcrt.dll
ModVer 7.0.2600.1106
Offset: 00033ec0

The following files are included in the Error Report: C:Docume~1JLocals~1TempWER61.tmp.dir00appcompat.txt
The other problems have been running slower than ever. Programs sometimes just close while running. There is a "Hmck?" or some sort of error every time I start the computer. (I'll have to restart it for the exact name of the error) I It just seems like this computer isn't running properly. It's a Dell Dimension 2350, about 7 months old. I have run virus scan and none show up.