Can't execute any .exe files

I downloaded some files earlier, and I think one of them was infected with a virus that is now on my computer. Whenever I try to execute any .exe files, I get a file not found error. I can still access IE by opening a .html file from my desktop, which activates IE. I have also managed to run regedit by renaming it from regedit.exe to regedit.com. I tried running the symantec sircam removal tool, but it did not find sircam. What do I do? What is the virus that is ingecting me and how do I remove it?

 

I'd run housecall.
Failing that, try the Exe fix

Daizy