When I change the setting of some applications in xp pro(like winrar , startup list ,Google preferences etc), they come back to their previous configuration when I reboot.
I have tried many things:
2)scanning for viruses with nod32 , scanning for Trojan horses with tauscan,checking for spywares with ad-aware , spyware doctor , antispyware
3)defragmenting disk with perfectdisk , cleaning registry with cleanmypc and registry mechanic , optimizing my xp with advanced system optimizer .
I also noticed that some registry keys came back to the registry after reboot , although I had cleaned them with some registry cleaners.