Contrary to all those who might think so...Windows does not need "tuning up" or "optimizing".
It needs users/owners who are willing to just do normal maintenace (chkdks /r and defrag) at the appropriate times...install proper applications for security (AV, Windows has a firewall which is adequate for many users, a program like SUPERAntiSpyware to assist installed AV).
Following link may be useful, it covers many basic concepts for maintaining a system: http://www.bleepingcomputer.com/forums/topic87058.html
The best thing that any user can do...make a backup of the system...when things are in good shape. Also utilize the Windows System Restore function to facilitate the hiccups that are going to come with daily use...do not rely on just one or the other...backup and SR should reduce the stress that so many users seem to self-inflict upon themselves...because they don't use these procedures.