Try to open any familiar applications like notepad or any images with "open with" again. Then choose the exact program. After that do a Restart. Your problem will be solved. Do let us know If You are still facing it.

I've already tried it but it doesn't work!its opened with Firefox again! :(((

I tried it recently and when I open notepad with notepad...then all of my programs at desktop or even in start menu are now opened with notepad! :( help me!

See http://support.microsoft.com/kb/2688326

Try this.

Go to Run Command (Start + R)

Type regedit in Run Command

Then Go to below path.

HKEY_CURRENT_USER_\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts

Then search for .ini

Delete hole .ini key or delete the userchioce key on that.

Then just Restart Your computer.