If your PC recognises the hard drive,why not delete a few files,and programs that you dont really use to get some space back,then defragment the drive,and reboot your PC.Dont just delete them from whatever your drive folder is called though.Use start,control panel,then Add and Remove programs from Windows.
Dont forget to regularly check your hard drive for viruses,spyware,malware,and the usual Adware nonsence.Another good program for removing junk is Crap Cleaner.Its freeware,and can be obtained from this link
http://www.majorgeeks.com/download.php?det=4191
You will be amazed how much junk your PC stores even when you've simply been browsing the web.Also use that at the end of the day.
Just a footnote,when you say you opened it,but it would'nt open,do you mean you cant access any files,or will no programs work?
Just see if you can get any of the advice I've given you above to work.If not,post back and let the forum know how your getting on.
All the best,
Nez.