NQC is a programming language similar to C (Not Quite C). It is included with the open-source IDE called BricxCC
). It runs fine on both Win XP and on Win 7 (32 and 64 bit).
The USB tower only works with a 32 bit OS, but the serial tower will work with a 32 or a 64 bit OS. Most modern computers don't have an RS232 port, so you would probably need to get a USB <> RS232 adapter in order to use your serial tower.
BTW, the Lego SW (as junk as it is) does work on Win XP, but I highly recommend using BricxCC and NQC instead.
I'm all for gun control... that's why I use both hands when shooting