What was the last version you tried? The newest? I've found lately when a new(er) OS like Winblows 7 comes out, it takes a few months to iron out the bugs with software. I believe you also need the latest version of dotNET winblows uses, but not sure on this.
I can't give a lot of advice on that, because I never switched over to Vista (thank god for small miracles!), and from all I heard about it, and Vista had been talked up quite a bit, I will not switch to Windows 7 for at LEAST a year! Funny how the "perfect" Vista was replaced within a year or so after it's release! Microsoft has a nasty habit of putting out half-baked OS's and then releasing a dozen "fixes" and "security upgrades".
I prefer to wait until after at LEAST Service Pack 1 or 2 ! (I know, you are forced to take whatever OS comes with a new computer....sux that way. I suggest when people ask, go TigerDirect and build your own! XP is pretty stable now! Gonna take a while for 7 to be!
Anyhow, check off and on with the Daz3d site, as they do release patches and fixes.
I will say, if you don;t have at least 1 GB RAM, it will slow down and/or freeze on you the more things you load. The more complex the scene, like character,props,background,clothing,etc...... the longer the load times and render times.
I have a P4, 2GB RAM, and ATI graphics card (an older one though)...and I have bogged down many times. A trick is to try to create the background first and render it, then load it as a backdrop or something. One JPG takes up less resources than say a half-dozen trees and a waterfall, all 3d objects! Try and create a scene in pieces, and then either reassemble or layer in Photoshop or other editing software.
Then again, I am poor...so I always try to find the poor-man's workarounds,lol! Starting to get good at it...kinda scares me! :D