I've only disk compression 1x on my old machine & programs came to a screaching halt, so to speak. When I got my new system, actually as of 2 systems ago, the guys that build my puters say it's not good to compress...so I haven't. Just got a bigger HD & use my space wisely. I'm now up to 3 HD's all 2 120's & 1 200. Just my experience. On my main HD I ALWAYS keep 1/2 of the drive space free, and I do mean always. I check space weekly & move/delete/backup as necessary. I've never had a problem operating this way. ~Knocking on wood now~ I actually have my Poser & Vue folders backed up twice, 1 backup on each HD.