This is for Windows XP
BlackViper's Windows XP Services Guide - PDF File (Acrobat Reader Required)
Using this guide will increase performance. Run XP-AntiSpy, Shoot The Messenger and Unplug n' Pray first before going through this guide since those utilities will disable some of these Services for you. Use the Guide in combination with the following list. If you are not 100% sure about a service leave it on its default state. The goal is not to turn off as many services as possible but rather to disable only unneeded services.
Instruction - Go to Start, Run, type "services.msc" and press enter. Left-click on the status bar twice to filter all the started service to the top. Double left-click on the Service Name you wish to change. Change the "Startup Type" to either Manual or Automatic, then select "Apply" and "OK", repeat for all of the following:
The following is a list of Services that you can Disable on most systems for increased performance:
Alerter
Distributed Link Tracking Client
Help and Support - (If you use Windows Help and Support leave this enabled)
Indexing Service
IPSEC Services
Messenger - (Shoot the Messenger and installing SP2 will disable this)
Portable Media Serial Number
Remote Registry Service
Secondary Logon
SSDP Discovery Service - (Unplug n' Pray will disable this)
Telnet
Upload Manager
Wireless Zero Configuration - (If you are on a wireless network leave this enabled)
The following is a list of Services that should always be set to Automatic:
Automatic Updates - (Required by Windows Updates)
Background Intelligent Transfer Service - (Required by Windows Updates)
COM+ Event System - (Required by BootVis and other Applications)
Cryptographic Services - (Required to confirm the signature of Windows system files, Protected Root Services and Key Services)
DCOM Server Process Launcher - (Required by Disk Defragmenter)
DHCP Client - (Required for Cable/DSL connections and Routers)
DNS Client - (Improves Internet Performance)
Event Log - (Required by Windows and cannot be Stopped)
Logical Disk Manager - (Required to manage and update your Harddrives)
Network Connections - (Required by Network Connections)
Plug and Play - (Required by your System Hardware, Never Disable This!)
Print Spooler - (Required by Printers)
Protected Storage - (Required to protected sensitive data and to prevent access by unauthorized services, processes, or users.)
Remote Procedure Call (RPC) - (Required by Windows, Never Disable This!)
Security Accounts Manager - (Required to store security information for local user accounts)
Security Center - (Notifies you of you Firewall and AntiVirus Status)
Shell Hardware Detection - (Required by the AutoPlay feature)
System Event Notification - (Required by various Applications)
System Restore Service - (Required by the System Restore feature)
Task Scheduler - (Required by the Windows Prefetcher, BootVis and Norton AV, Never Disable This!)
Themes - (Required by the new look of Windows XP)
Windows Audio - (Required for Sound)
Windows Management Instrumentation - (Required by Windows, Never Disable This!)
Notes - Windows Updates can enable services that you have previously disabled. Check which services are running after a future Windows Update is completed. If applications stop working after using this guide it is usually due to being to aggressive with disabling services. Enable the services you disabled one at a time until the application works. In the future leave this service on automatic. If you run into any problems set all services back to their Defaults and start over.
More details : http://mywebpages.comcast.net/SupportCD/OptimizeXP.html