If you like a sleek and fast everyday computer then follow the steps here. None of the steps will take away any features of windows that are nessesary, so your computer will still be fully compatible with whatever comes:
Major - 5x to 10x times improvement
The network in Windows are made for sending and recieving huge loads of data, but when it comes to small chunks that you like to sent very fasts, for games etc., you dont want the packages to be delayed. Use the TcpAckFrequency to improve your gaming "ping time" with a factor of 5 - 10 times, or from 300ms -> 30ms.
1. TcpAckFrequency: You will games will be more playable, especially FPS, WOW arena etc.
Major - 1x to 3x times improvement
Windows are made for old plate based drives and it does a lot to keep those old plates busy. Because plates are slow, when it comes to search time, Windows are doing optimization all the time. On SSD drives we do not have the same issue, since all file access is the same.
2. SSD optimizing: Your computer will boot faster, programs load faster, the SSD drives will last longer.
Minor - 1% to 10% improvement
The last and no so nessesary thing you can do to improve windows is actually to disable some logic that keeps you processor from using all cores when not nessesary. What you do is to enable all of them all the time. The power usage wont differ so much if you have a later processor type like fx sandy bridge type. On slow system the improvement is notisable, on fast systems its mostly in benchmarks you will see a little difference.
3. Core parking: Your computer will be more responsive.