I had similar problems once, 1) Are you defragging enough? 2) You might have too many programs running, this can be tough, try to run only the bare minimum programs, uninstall what you don't use. 3) Running lots of video usually means defragging more often. 4) Do a lot of programs run when you restart, you might try to reduce what runs when you start up, helps speed things up. 5) Do you know what level of defragmentation you are at? I always try to keep mine above 89%.
I have the same issue as you when it comes to music on the hard drive, lol, I never want to delete anything.
Also having only 200 MB free space available is not much today. You might try a memory upgrade if possible.
The more you have on your hard drive, the more the PC has to think, and thus run slower. The less it has to think about the quicker it gets and nicer in general.
Hope this helps. Good Luck.