Installing a Windows 2000 modem driver (and not an XP one) on WinXP will make the modem run faster, but when I say faster I mean that XP restricts the max speed to 44.1 - with the Win2000 driver, you may if you are lucky get 48 or 50Kbps - however, this will only save you about 15 mins on a 48 hour download.
I started this game with a dial-up account and switched to dsl a month ago - the funniest thing that got me after swapping over - the in-game lag is still just as bad on DSL as dial-up..... I think you need a direct 1G connection to the server and I'll bet it will still be laggie as hell.... What a rip-off...