how does your maya "lag"
is it the viewports, the displays are bad?
or it lags when it loads and when u use maya's tools.
if its the latter, then i suggest getting more ram.
but 512mb is adequate to run maya. i have known ppl to run maya on 64mb of ram. i am running it on 1.5 gig of ram, pc133, they are very slow ram, so its about 512 mb considering the standard ram today, and i get no lags at all. [unless i do something stupid]