Snow_Patrol :
I wouldn't bother with emulators, because at some point in time you'll run into something that requires a proper component of XP.
I used the term "emulator" in my post because that's what the OP chose for the thread title, but in fact I was referring to the Virtual PC version that is integrated into Windows 7 (although it's a separate download).
Windows 7 also has a "compatibility mode" which does NOT use a virtual machine, but rather allows you to set characteristics of the programs runtime environment (API calls, etc.) to more closely match XP.
If you have a program that doesn't run under Windows 7, you should try using compatibility mode first, and if that doesn't work then you can try running the program in an XP virtual...