If its Windows 7, if you didn't format your drive when "fresh" installing the Windows 7 installer will detect that there is an existing install of Windows on the drive and it will move all of those files to a folder called "Windows.old" on the C drive. Check your C drive for a folder with that name and you will have an answer. You can delete that folder and it should free up lots of space. If thats doesn't work you should get something like a linux based partition editor and format your drive. Then go back and fresh install windows again with a completely clean drive. This can be done much easier if you have another pc nearby which you can throw the drive in and format that way.
Hope this helps.