Windows installs drivers required to load on the PC you originally installed it on. Booting it up in another PC sometimes works, sometimes it results in BSOD's (Blue screen of Death), other times it doesnt work at all.
If you have a local electronic/hardware store near you, you can either pick up the conversion adapters or cables for around $15-25.
Best bet is to hook it up as a slave drive (a secondary drive on a computer that already has Windows installed) so that you can access the data that way.
If you have Vista installed, you won't be able to access your personal documents without some additional software to remove the security.