Adding Serial Ports to your Computer can be very easy or a total nightmare! A lot of our calls at Split Second are related to this issue.

In an effort to make things easier Split Second now sells a very simple USB to Serial Adapter and a simple mini 4-way USB hub. They are $30 each.
These have shown to work well with XP and 2000, with the software and in combination. So, you could add the hub, throw your USB Software Key on the hub and 2 of the Serial adapters and you can run the Key, the Timer, and a Scoreboard out of one USB port...

These devices say they support Windows 98SE but as far as I can tell USB only actually works well with XP and 2000.

Geoff Elder
http://www.SplitSecond.com
http://www.SplitSecondRealTime.com