Sounds like your exe association dissapeared. Try:
Download exefix_xp.com utility and save to Desktop. Double-click the file to run it. This utility fixes the exefile association in the registry automatically.
Additional tip: To run the utility silently (without any prompts), use the -silent parameter. Open a Command window (Command.com) and type:
C:\Utilities\exefix_xp.com -silent
Assuming that the exefix_xp.com is placed in the C:\Utilities directory.
OR
Download combofix after download rename the file to combofix.com or some other extension then .exe. Let combofix run and your problem should be fixed. It worked for me. Or you can run your maleware program but you have to rename the extension.
