Windows File no applications associated with file

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

http://support.microsoft.com/kb/950505#LetMeFixItMyselfAlways

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.