WinXP sp2: check (since BF2 doesn't run on win2k, grrr). But since the game runs on the same engine as Pirates2, I'm sure civ4 will run on win2k as well.
Athlon 2600+: check (it even runs on 2086mhz these days
)
Geforce 6600 256mb: check
SB live!: check
DVD: check
HD space: check. Unless 2k games are as moronic as the EA games whores: those MF assholes (insert more profanities here) require to have 1600 MB free space on the c-partition, because you can't run a patch otherwise. Ever heard of changing temp folders to another partition, assholes? (yes, I'm angry)