Adobe Reader
http://get.adobe.com/reader/
Allows to open any files that have a .pdf aside. Be sure to update it regularly!
Finale Reader
http://www1.brothersoft.com/finale-reader-197633.html
Allows opening of files with .mus aside it.
WinRar
http://www.win-rar.com/index.php?id=postdownload&dl=/rar/wrar400.exe
Allows opening of files with a .rar aside it. To use it, right click that .rar file and click "Extract Here".
