Can you use the primary hard drive from one computer as a second hard drive in another and still use the programs on it?
Mostl likely no:
you will need to reinstall most programs anyway.
Older programs will work (they usually don't need installation but might get some trouble:
ex unreal tournament 1 (old game)
but Microsoft office and any newer like adobe reader, java will need to be reinstalled.
Steam on the other hand would work but will update before running properly.