Computer problems need help?

I got some issues with my pc. For some reason the drives aren't loading either errors or missing files inthink or something and I can't get into windows. I don't know how the drives could be bad they werenkinda new. How can I fig out if windows is corrupted or if it's just bad hard drive. If HD is bad is there a way I can have them be slave drives. Is there a god prgram I can get to transfer files from my hds to my external. How do I make sure that the master is loading right. Since buying win 7 would the best thing be just get a decent HD size and start over