Doing a search in GameFAQs, I found a tweaked game.ini which by many users' feedback has been reported to make the game have no or very little lag in systems even below the MINIMUM specifications.
You can download it here:
http://www.koevis.demon.nl/GAME.rar
Make sure to backup your game.ini file inside your Boiling Point directory before extracting the one in the archive.
Some additional notes, having 512 or 768 MB of RAM can really do bad in the game. This game requires 1-2gigs of RAM to play on the highest standard. A little trick would be to raise Minimum and Maximum Page File to 1500-2000MBs (if you have that much space left on your disk.) Don't ask me on how to do that, use Windows Help for once!
Try these and tell me if it works.
Sorry for the off-topic mods, feel free to move it.