Just out of curiousity, why are you alt-tabbing out? Most games I've played don't like to be alt-tabbed out of but I think that's more of a Direct X issue than anything else. As a general rule I never alt-tab out of a game because more often then not something gets screwed up when I do.
with 2gb of ram alt tabbing is no problem.
i have run things in the backround that i check up on a lot, for example teamspeak, trillian and itunes.
i alt tab to:
reply to IMs I get on trillian
skip a song in itunes
switch channels in teamspeak
+ various other things.
I'll often take a break of playing and leave warcraft runnig and connected to battle.net.
when ir eturn to my PC i won't want to jump right back to wc3 rigth away and will check an email or what not
i alt tab all the time