[unicorn]

Sound like a viiri after all.
I have found two other possible solutions for you:

1:

Code:

Copy and paste the bold text below to notepad and save as exefix.reg. Double click on it to merge with the registry, It will repair your altered .exe file association. Run a full system scan afterwards.

REGEDIT4

[HKEY_CLASSES_ROOT\exefile\shell\open\command]
@="\"%1\" %*"

2:

Code:

Just run this YahaRegfix.com tool offered by Solo Antivirus. It will fix the registry entries. You can get it from the link www.srnmicro.com/downloads/YahaRegFix.com After that you can run all .EXE files

Theese solutions came up after some googling and refers to somebody fixing a problem after having been infected with trojan: Backdoor.OptixPro.12
Do you happen to have installed Winamp 2.9x recently?