|I would NOT recommend doing that with Windows 7. Even though you may be using the latest build, which hasn't been determined, you still have a greater fisk than normal of something going wrong.|
25GB should be MORE than enough space for any OS. Your problem may be that you are installing other programs to that partition. Just install them on the other partition. You can also store your music, pictures, movies, etc on the other partition.
BTW, you do keep at least TWO copies of all your personal files, don't you?