It looks like some free space on my Gateway Hard Disk Drive has been magically hidden since after I installed Windows XP. Is that a feature Micro$oft provides, removing 20+ GB of your HDD space free of charge?
It reports a 250 GB drive, of which cca 45 GB are used, but says free space is just cca 185 GB. WTF?
The first thing you want to do is make sure your drive is formatted OK. Get a HD manager tool like Partition Magic or something, and have it check your drives for formatting errors. It can re-format it if necessary without damaging your files, so it should be an easy fix.