One of the most viewed Security Garden pages is
Ad-Watch Setting Can Kill .LNK and .EXE File Extensions. Although published in 2006, it still receives a dozen or more hits daily. That being the case, I can only suspect that users are still using the "Automatic" setting with the election to "Lock executable file associations" in Lavasoft's Ad-Watch.
Default file types such as .lnk, .exe, .com, etc. are system file types and should not be associated with any application. Windows knows how to handle those file types so why Ad-Watch breaks the associations when supposedly protecting them remains a mystery almost four years after the problem was first discovered.
It is apparent that many applications attempt to associate those system file types with their program. As a result, Microsoft MVP, Ramesh Srinivasan of Winhelponline, created registry fixes for Windows Vista to repair the some of the most common types of file associations.
To fix the association for a particular file type, download the corresponding fix from the links table at File association fixes for Windows Vista and follow the provided instructions. (Note: you need to be an administrator to apply the fixes.)