run msconfig and stop all those unecessary background programs - which is most of the icon cluttered systray. Be sure to keep the MS ones tho - nearly all you need for now, although even those could be pared down eventually. For now zap most of the others - get brutal, but watch you keep firewall/AV / MS going initially.
Stop firewall & AV if playing off line
Boost swap file to 2Gb
This and all the others in preceeding posts are small in themselves, but add them up and you start saving a chunk of RAM and some cpu time - all helps give more room to breeth for GalCiv.
The most effective without a doubt are the graphics changes the others outlined, eye candy is nice, but pointless if game becomes unmanageable for you due to taking resources to keep up eye candy.
Lastly - the old adage - update drivers, it does make a difference in the long run.
Regards
Zy