[shrimply]

Well having just upgraded from 1 gig, I can tell you a few things although I'm no expert.

Vista runs OK on 1 gig, I have done for nearly a year, so if it is just basic word processing and things it shouldn't matter too much, bigger applications, will require a bit more RAM, not had a chance to try much out yet but the media centre is running much more smoothly when I'm viewing TV.

If its somewhere like Dell and its going to cost you a tenner or something similar to stick in an extra Gig then I personally would. Luckily my new stuff worked but it can be difficult, although if you've got the people here behind you not much can go wrong in computer world.

If its a shop and they're going to charge you a larger amount for the upgrade, I do it yourself, my RAM cost £14 and its not hard to fit.

I'm sure the experts will give you more in depth answers though.