**Plutom - I have 1GB RAM & I use Poser 7 & Vue 6 Infinite.
**Within Poser I can work well with two figures & plenty of clothing items. Putting a third figure in & the scene will slow down.
Within Vue I can work comfortably with two figures just like I do with Poser. Same again though, add a third character & it can be a pain. In Vue it's best to purge the memory after every import. 
Also, (this applies mainly to Vue but does help in Poser as well with not much memory) is to after you've loaded your figures & set the scene up, shut down the program & reload it as this will free up memory again.
Another thing to remember when not havimg much memory is to try & not have memory intensive programs running in the background. Having Poser & Vue running together, internet explorer, virus scanners etc.
Also, just remembered, one of the biggest things which uses memory in Poser & especially in Vue, is texture size. If you're having characters in the background where detail isn't needed then you can reduce the textures in your paint program before the import. I personally don't do that as I'm stubborn & like to get in as much detail as I can even though it may mean it's harder to work with!