I love Linux, I truly do, but I just hate Debian. I'd like to get 40 GB back to use for Windows.
Never been able to get Debian to work out well for me, more of a Fedora person.
I've not actually used Debian, but I've used Debian based systems(aka Ubuntu(the shame, I know, noobtastic, but it's easy to use when I'm not using Arch)), what exactly is it about Debian you hate?
If your linux partition is formatted to ext3 or ext2, which I assume it probably is, you may need to go to great lengths to make Windows read and write to it. There are some utilities available that let Windows do this, but I've had sketchy results with every one I've used.
Easiest option is probably formatting, but I would assume you can simply load a livecd of some kind and delete everything, depending on how you have your drive partitioned.
I have Debian on 1 partition, and Windows on another.
Don't suggest formatting. I have WAY too much to back up, and not enough storage to do so.