Windows losing file associations, windows XP and Vista.
I have seen two systems lose file associations with .exe after being on line in the last few days one windows XP and a windows Vista.
There was a loss of some applications at startup and applications requiring a .exe would not run.
Microsoft had a fix for windows vista
I managed to find a reg file to repair windows XP registry settings for file associations I used "xp_exe_fix.reg" downloaded from http://www.dougknox.com/xp/file_assoc.htm.
Neither user said that they had been prompted to download a file, which they had tried to stop.