I was watching azuritereaction stream once, and as he was going about his computer, he noticed he was losing space and mentioned the name "SpaceMonger." I decided to look it up, and it is actually a really nice program. It hasn't been updated in a while, but it works fine with my Windows 7 64-bit computer. It shows files by location, size, etc. Accumulations in certain folders. It is very useful.
http://www.sixty-five.cc/sm/Edit: Well the way he wrote that confused me. Desktop seemed obvious for the main desktop, but he was talking about moving things and space so I was like "Wait, does he mean storage space?" I stand by this post though - You could use it to locate bad programs you don't want anymore and uninstall them, which might also clear up the desktop. :P