Hi
What do you mean by disk usage?
Do you mean that you don't have a lot of disk space left?
What it the size of your drive, and how big is your Windows install?
If that's the problem there are a lot of things you can do to make the install smaller.
Try downloading and running Winderstat, it will tell you what's using up the disk space.
http://windirstat.info/ For me one of the things that was using a lot of space was my System Restore Points, (about 20 Gigabytes) and the fact that I was using Quick Start, (another 27 Gigabytes).
Turning off both of these saved me a ton of disk space.
You can also use CCleaner to remove the Windows.old files, (about 10 Gigabytes).
Mike