You might want to include the specs of the system you're working with and the game that you're trying to tax the system with. Otherwise you're only going to get a bunch of questions and not much constructive feedback from the community.
Also depends on what game and if its online, many different forms of lag.
2gb isn't a lot of ram, I can't remember last PC I owned that had that much, maybe 14 years ago? So it sure could be the reason.
Closed thread since all the responses are lackluster and pointless. OP, if you want to reopen the thread, please PM me and please make sure you have substantial information to parse to this thread in order to let the community answer your problem.