1) Download Q -- a free emulator on which Windows can run. There are other similar programs, but I think it's one of the better ones.
2) Find and purchase a used copy of Microsoft's VPC
3) If you have a Windows computer, enable remote desktop sharing and then use the Microsoft Remote Desktop Client to log into it.
Option (3) is the only one that will provide very usable performance. I have an old copy of VPC with Win2k sitting around somewhere... it's much faster than Q, but still brutally slow.
I have an iBook G3, and I've used Remote Desktop with my Thinkpad to much success. Provides a quick-fix if windows is needed for a small task alongside OS X. My iBook also runs 10.3.9, so this may be a good option to seek.
Beware, though. Remote Desktop Connection requires XP Pro to use most easily.
Yeah, if you have access to a real Windows device, Remote Desktop is absolutely the best option. You can do very usable Windows over the network, even over the public internet, from a relatively old computer.