SP3 is slow

My XP SP2 is was running good but after installing SP3 the whole system is slow. I have

1. Checked for viruses/malware using Malwarebytes anti-malware and SAS
2. Checked unwanted applications during start-up using - msconfig
3. done a registry clean and repair
4. Uninstalled any applications i don't use/want
5. Defragmented the hard drive.
6. moved virtual memory on another HDD
7. checked if my pc is overheating - it isnt
8. disabled anti-virus scheduled updates - same problem, so turned it back on

9. used ccleaner
10. Kaspersky tune up utility repair and compact registry and everything else it offers

i am still having the same problems, the only thing i can think of is to uninstall SP3 ?

I think Microsoft is trying to use xp sp3 to overhaul the security model like vista but vista is slow any way. There are many top-range pc's where i work and using XP is fast; using vista on these top range machines is slow.

without the Areo glass and all its effects and the sidebar in vista, with IE7 and UAC, vista is just xp, so MS is just trying to ploy users into upgrading to vista because SP3 tries to overhaul xp into vista midway without the aero gui

I think if i should use this rule (of philosophy) If it ain't broke don't fix it! and uninstall SP3