My C: drive is running low in it's space. So, i guess mounting the program files will help me. But how can i mount them to a different drive ?

Either you uninstall some of applications to give free disk space in C: drive, or install them into D: drive. You can't physically move the existing applications in Program Files folder into D: drive; this will result in blue screen.

Well, i didn't get mounting ways. So, I used partition magic to allocate free space from other drives to drive c:. This was easy to go with method.
Simple to use and result in no time.