I think it best though to only defrag after you do a installation, or put a large file on your hard drive ect. Alot of these tips are good and I use them as well. They are mentioned in a ebook I read, which I recommend. TGTC for Windows Vista. If you do take the advice in this book make sure you read up before you start removing everything though.

I have all my games disable visual theme and desktop composition though
Once I exit them it goes back to aero which is cool.

I even heard of people starting their games, alt tabbing to the desktop.
Cntrl+Alt+Delete and ending the explorer.exe. After done playing Cntrl+Alt+Delete, run new task: explorer.
I haven't tried it yet though, to know if it helps.