• Alerter: Is mostly used on networks/ Active Directory domains to notify selected users of Administrative Alerts.
• Automatic Updates, Background Intelligent Transfer Services: These are the components of Windows Update and you should not disable them unless you don't want this service.
• Clipbook: Never used it. Has something to do with sharing information.
• Help and Support: This is the Windows Help and Support center. If you're planning to use Google to search for answers you can disable it.
• Messenger: Should be absolutely disabled. As a matter of fact in Service Pack 2 is disabled by default.
• MS Software Shadow Copy Provider, Volume Shadow Copy: Has to do with shadow copies which is a very cool way to backup files and access previous version of them. However it can be used only in Windows XP Professional in an Active Directory Environment with Windows Server 2003 and needs a "previous version" software to be installed. Most of the time useless.
• NetMeeting Remote Desktop Sharing: Nobody uses that.
• Remote Desktop Help Session Manager: If you don't plan on using Remote Assistance disable this service.
• SSDP Discovery Service, Universal Plug and Play Device Host: Used for Universal Plug and Play devices which is a concept that has to do with computers communicating with intelligent appliances to order food and such. Useless for now and a big security whole in XP SP1
• Task Scheduler: Used to schedule applications to run at specific times. If you don't do things like that on your computer disable it.
• Themes: This is responsible for that cool Windows XP look. Without it your interface will be like in Windows 98 but it also eats a lot of resources.
• WebClient: Not very clear what it does but if you disable it you will not disable web browsing.
• Wireless Zero Configuration: If you don't have an wireless adapter you don't need it.