Yeah, compression tools like Drivespace put a lot more stress on the HDD and certainly on the CPU. You might be able to put 1.5 to 2 times more data on it, but at what cost?
Programs will load terrebly slow.
A better Idea is to compress a small piece of you're HDD to put text-files and so on. Put you're operating system on the uncompressed part as well as often used software.
Also do not put mp3, or any compressed file on the compressed volume (since you can't compress those any further)
Godim