I just freed 16 GB on C:, mostly by disabling hibernation (which doesn't work with >4gb ram anyway), moving the windows search index (>6 GB!) and My Documents (another 4 GB).
Determining that those directories were the biggest space users was pretty easy thanks to the tool WinDirStat which is very useful when trying to figure out where all that free space went.
Coding-wise I haven't done enough recently... I don't quite know where to start with the menu/hud system coding, or at least I keep telling myself so.