Almost all file types in Windows are associated with applications. This association can be changed by right clicking on a file and selecting the required program from the “Open With” option. It can often be quite a hassle to disassociate files once they are tied to a specific program. As a system administrator I once received a ticket (in my former job) to resolve an end user issue of a language trainer who was having problem opening an Excel file. On arriving at the training room, I found out that she had associated the XLSX file with MS Paint. Duh!
Unassociate File Types is a portable application which allows easily removing file association with default programs. This can be handy in unassociating files which may have been accidentally associated to a wrong application or to simply removing default program associations.
Just launch Unassociate File Types, select a file extension and click Remove File Association. This application requires administrative privileges to work so makes sure that you are logged in with an Administrator account.
Unassociate File Types works on Windows Vista and Windows 7.