Assuming Windows XP check:
http://www.blackviper.com/WinXP/servicecfg.htm
There is a complete tweaking guide here:
http://tweakhound.com/xp/xptweaks/supertweaks1.htm
You could download http://free.antivirus.com/hijackthis/ also and post a log here, someone can thet tell you whats safe to turn off.
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