I just got a Windows7 computer and find that a crucial program to my business only runs on WindowsXP.

So can I put the old hard drive in my new computer so that I can run the program that I need? If so, I presume that I'd need to change the jumpers on the old hard drive. What else do I need to know?

Alternatively, could I just get an "enclosure" for the old hard drive and use it externally?

Thank you!

Sure you can install the drive and see the contents but you won't be able to run the program from that drive. That would only work if you set up the computer to dual-boot Win7 and XP.
You can try reinstalling the program in Win7 (if it allows it) in XP compatibility mode: [Win7/Vista] Windows XP Compatibility Mode in Windows 7 and Vista | UNC-Chapel Hill Help and Support

Have you tried to install and run that application in Compatibility mode yet under windows 7? NK beat me to it by only moments.

I didn't know about compatibility mode. I'll give it a try and let you know how it went.

Thank you, NeedKarma and Smoothy. The program is partially working using compatibility mode, but has some issues... so now I'm going to try to run it in XP mode. If that does not work, the next step would be "virtual pc", but I'm thinking I don't want to go that route. If the program does not work in XP Mode, then I'll have to get new software.