If you are a hard core gamer then the tweak below is for you. Below are a list of windows services that are recommended you change to the manual setting.

Routing and Remote Access
Alerter
Application Layer Gateway Service** (only if firewll is not used)
Application Management
Background Intelligent Transfer Service
ClipBook
COM+ System Application
Distributed Link Tracking Client
Distributed Transaction Coordinator
Help and Support
IMAPI CD-Burning COM Service** (only if do you not use the cd-rw xp record suport)
IPSEC Services
Logical Disk Manager Administrative Service
MS Software Shadow Copy Provider
Net Logon
NetMeeting Remote Desktop Sharing
Network DDE
Network DDE DSDM
Network Location Awareness (NLA)
NT LM Security Support Provider
Performance Logs and Alerts
Portable Media Serial Number
QoS RSVP
Remote Desktop Help Session Manager
Remote Procedure Call (RPC) Locator
Remote Registry
Removable Storage
Server
Smart Card
Smart Card Helper
SSDP Discovery Service
System Restore Service
Telnet
Themes
Uninterruptible Power Supply
Universal Plug and Play Device Host
Volume Shadow Copy
Windows Image Acquisition (WIA)
Windows Installer
Windows Management Instrumentation Driver Extensions
Wireless Zero Configuration
WMI Performance Adapter
Fast User Switching Compatibility ** (only if fast user shiching is not used or the machine have one user only)
Protected Storage
Windows Time
TCP/IP NetBIOS Helper
Task Scheduler
Secondary Logon
Print Spooler ** (only if the pc do not have or use a printer)
Indexing Service
Error Reporting Service
Computer Browser
Internet Connection Firewall (ICF) / Internet Connection Sharing (ICS)

System Restore Service
Themes
Universal Plug and Play Device Host
Windows Installer
Windows Management Instrumentation
Windows Time
Task Scheduler
Error Reporting Service
Computer Browser
Internet Connection Firewall (ICF) / Internet Connection Sharing (ICS)



this is a list of services that i would reccomend you do NOT turn to manual, unless you know what they are and what they do, and can run your computer without them, the reasons are as follows...

Also if your pc is part of a domain, or a large network, especially in a coorporate office, i reccomend not disabling a lot more of these services...

System Restore Service
-critical system restore in case of a computer crash emergency etc... also note that you cant just start the service after the problem occurs, it must be started ahead of time, and a restore point made on the computer.

Themes
-Ms themes, if you dont like the look and feel of windows calssic, i wouldn't turn this off...

Universal Plug and Play Device Host
-This one is only in the do not change section because... you CAN turn off the Universal plug and play device HOST, but, let me warn you that if you disable Plug and play in general, you will have a great many problems on your pc

Windows Installer
- if you want to keep installing those games, i reccomend you do not switch this.

Windows Management Instrumentation
- For all of the power users and admins out there, you know as much as i do, that this can come in handy from time to time. Breakdown of descriptions of this service, found on :
http://www.theeldergeek.com/windows_...umentation.htm

Error Reporting Service
- If you want microsoft to continue to make improvements on both xp and vista, you should leave this on, and report the errors.

If you have any responses, please post them, if you found something i posted that is wrong, please tell me.

Actually you are both wrong

Windows installer is manual by default. If you change it to auto or disabled then you will get an error that the windows installer service is not running or that they is an install already in progress. It starts and stops as it needs.

also you dont know what you are saying


You can turn off Universal Plug and Play Device Host safely. It has NOTHING TO DO with plug 'n' play with regards to hardware. Universal Plug and Play (UpNp) is a networking technology for discovering routers, xboxes etc...

However, you are right in that you should never turn off the "Plug and Play" service or else the vast majority of your hardware wont work.