The make of PC is no big deal, but I would suggest you get something that can run Win7. The guys who make the software for timing, are moving past WinXP since it is no longer being updated by Microsoft. Win8 is more for mobile devices (and is a pain) so I don't recommend it.

The serial to usb adapters are fine, you need to use the right drivers. I have purchased this one, (Sabrent) and it works the best with drivers from 2008.

I would also look into upgrading to RC4 as soon as possible. RC Scoring Pro is offering a trade in for 700 bucks. RC2 will not see the RC4 transponders.

Good luck, anymore questions, just ask.