|mehwish, Go to the link below and download the applicable file association fixes , unzip them, then run them. Instructions are on the page.|
If you can't run those reg files do the following for each one:
Press CTRL-ALT-DEL and open Task Manager. Once there, click File, then hold down the CTRL key and click New Task (Run). This will open a Command Prompt window. Enter REGEDIT.EXE and press Enter. Once regedit is open click File>Import and locate one of the reg file fixes, hilite it and click Open. Do this for each of those reg file fixes.