With your size of hard drive set it at whatever. If you dont want to use VM, get another gig of ram. And to get to it, you go to control panel> system> advanced > settings >advanced > change.
Mine's at 8 gigs, no reason really, just cuz i could, i have too much space as is. I doubt it does anything more than if i had 3gigs worth, but it's not wasting any space, i've only used 47 of my 250gigs on my hd.
I increased mine to 3gigs but I only have 512 of actual RAM. Is this a good idea because I heard windows will use the 3gigs of virtual ram more than the actual ram and I heard it will run slower.