I have a Dell XPS M1530 laptop with a 320Gb HDD. It came partitioned as a main C drive with a recovery D drive.
It had Vista on it to start with, but I have just done a what I thought was a clean install of Windows 7. Windows is showing the size of the C drive as 285Gb of which it says 192Gb is free, so 93Gb in use.
Fair enough you might say. However, when I add up the size of all the folders on the drive, including hidden ones, I only come to roughly 48Gb, which means there is a discrepancy of 44Gb. Some of that will be the swap file, but still it seems like a huge difference.
More aboutwhere hard drive space gone
How much space is decated to system restore? and there is the elusive voulme shadow copy....
Try running disk cleanup (just type disk cleanup in the start search).