Computer Browser: If your system is not in a network, you have no need for this service and you can disable it. If you are in a network, but do not habitually browse the network for file shares, you can also disable this service. Disabling it does not stop you from accessing file shares on other computers, it just prevents you from using my network places to browse to them. Mapped network drives and direct connections (i.e. \\mycomputer\myshare) will still work.

Distributed Link Tracking Client: This service maintains links to NTFS files that are moved between disks or computers. Generally not needed except in larger networks, so you can set to manual. I wouldn't recommend disabling it.

Error reporting service: Like E.T., it calls home to Redmond if a program crashes unexpectedly. If you have a social conscience you can leave this enabled. Otherwise disable it.

Indexing Service: This can have a major effect on system performance if activated (though it does make file searches quicker, if that's your thing). The best way to remove it is not through services.msc though. Instead go to 'my computer', right click on each NTFS drive you have and choose 'properties.' Now disable the 'allow indexing...' button at the bottom of the 'general' tab.

Messenger: Allows simple communication between networked computers by means of pop-up text windows. This service is the source of those irritating pop-up desktop ads that flooded the computer world a few years ago. One of the improvements Service Pack 2 introduced was the disabling of this service by default. If you are running pre-SP2 Windows XP or Windows 2000, disable this service immediately.

Net Logon: Used for logging into a Windows domain. This is not required in a typical home network, and if you need it, you'll know. Disable.

Net Meeting Remote Desktop Share: Allows remote control of your computer through the netmeeting application. Sound appealing or useful? Leave it at manual then. Otherwise disable it as a potential (though currently unproven) security risk. Paranoia is a healthy trait when it comes to your computer…

Network Provisioning Service: Not required for home networks; disable.

Performance Logs and Alerts: Disable unless you want to measure the performance of your system using the performance monitor application.

Qos RSVP: Disable for normal networks. May be required for netmeeting.

Remote Desktop Help Session Manager: Has anyone ever used Windows XP's remote desktop help feature? We thought not. Disable this.

Remote Registry: Enables remote registry editing on your computer over a network. Why would anyone want this enabled? Beats me. Disable.

Secondary User: Allows access to the 'run as' command in the right click menu of application executable files. This command allows you to run that particular program as another user. This is a potential security hole for managed computers, and if you can't think of a good reason to use this feature, disable the service.

Server: This service allows you to share files and printers from your networked computer. If you don't want or need to do this, disable the service.

Smart Card: Enables the use of smart card authentication in Windows XP. Disable unless you have a good reason not to.

System Restore Service: If you decide you want to disable system restore, use the instructions in that article first, then disable the service.

TCP/IP NETBIOS helper Service: Safe to disable on most home networks. If you experience connectivity problems, restore it.

Telnet: Remote console connectivity. Disable unless you know you need it.

Terminal Services: Disable unless you plan to use Windows XP Professional's remote desktop feature .

Themes: This service provides the 'look' of the Windows XP desktop and toolbars/menus, complete with various graphical effects. Disabling it will make your desktop faster, but it'll also make it uglier. Stop this service for a preview, it won't do any harm.

Uninterruptible power supply: You don't need this unless you have a UPS attached to your system, and you may not even need it then. Disable unless you know you need it.

Universal Plug and Play: Switched to manual by SP2. If you do not use SP2, we'd recommend you change this service to manual anyway.

Webclient: Allows FTP-like access to hosted folders and data on websites. May be useful for other things too, but not really necessary as far as I know. Disable unless someone give you a good reason to do otherwise.

Windows Audio: Can be disabled if you have no soundcard. Otherwise leave as is.

Windows Time: Automatically synchronizes your computer's clock with a Microsoft time server at weekly intervals. You can disable with no major ramifications unless you use your system as an alarm clock.

Wireless Zero Configuration: Helps automatically configure wireless devices. No wireless devices equals no need for this service.