The best way to keep your computer clean and fast.
1) make fresh windows install
2) apply only necessary update or fix
3) make disk defrag
4) install your driver(motherboard, video card ....)
5) make disk defrag
6) install your daily use software (only the required one as winrar ,FireFox...)
7) make disk defrag
clean the registry
9) kill unnecessary service
10)make a back up using Norton ghost for example or Acronis
If system slow down or for some reason you have any problem just make a restore.
and u are back to a clean fast optimized windows with just two click.
The hole restore process in my case take about 2 min .