Where is the lag coming from?

[Crono]

I used to have an hp pavilion @ 800mhz celeron. No problems for me, though it was crap.

Maybe your computer is having a hard time loading the gmap? Or maybe the gmap+tileset+the real lag+the amount of players = lagging you up?

This is kind of stupid but update drivers and everything first. Then go to audio and turn up the voice a tiny bit. (Make sure it's not all the way down, it kills frames for some strange reason).

You can also try to turn off light effects and mess around with the UDP option?