1.) The deciding factor is going to be the CPU speed. It should be 1000 MHz (1 GHz) or faster.
2.) The minimum amount of RAM should be 512 MB. The PC does not have to have 512 MB installed as long as it can be upgraded to at least 512 MB.
3.) The hard drive should have a 20GB or better capacity.
4.) It should have the standard components: CD ROM drive, Floppy drive, Network Interface Card.
5.) The computer should be in good working condition.