Installed On 2 Hdds, Get Programs To Work From A Secondary Hdd?

i put together a system the other day after my old one totally pooped out on me. i installed the hard drive from my old system into the new one as a second hard drive, and installed xp pro onto a different hard drive (primary master) in the new system.
how can i use all my old programs that are installed on the old hard drive without confusing the heck out of xp? many of the applications on the old hdd are confused when i run them, i am guessing because when they reference files in locations where they think they should be, but they are not finding them. i don't even have enough room on the primary master drive to install all the programs, its a very small drive. nor do i have enough room to fit xp onto the second hard drive.