Some possibilities are:
Alerter - Sends alert messages to specified users that are connected to the server computer.
Application Management - Allows software to tap directly into the Add/Remove Programs feature via the Windows Installer technology.
Background Intelligent Transfer Service - The Background Intelligent Transfer service is used by programs (such as Windows AutoUpdate) to download files by using spare bandwidth.
Clipbook - ClipBook permits you to cut and paste text and graphics over the network.
Error Reporting Service - Allows applications to send error reports to Microsoft in the event of an application fault.
Fast User Switching - Windows XP allows users to switch quickly between accounts, without requiring them to log off.
Help and Support - Allows the XP Built-in Help and Support Center to run.
IMAPI CD-Burning COM Service - You don't need this if you have other software to create CDs.
Indexing Service - Indexes contents and properties of files on local and remote computers; provides rapid access to files through flexible querying language.
IP SEC - Manages IP security policy and starts the ISAKMP/Oakley (IKE) and the IP security driver. If you are not on a domain, you likely don't need this running.
Messenger - Transmits net send and Alerter service messages between clients and servers. This is how a lot of pop-up windows start appearing on your desktop.
Net Logon - Supports pass-through authentication of account logon events for computers in a domain. If you are not on a domain, you don't need this running
Network DDE - Provides network transport and security for Dynamic Data Exchange (DDE) for programs running on the same computer or on different computers.
NT LM Security Support Provider - Provides security to remote procedure call (RPC) programs that use transports other than named pipes.
Performance Logs and Alerts - Collects performance data from local or remote computers based on preconfigured schedule parameters, then writes the data to a log or triggers an alert. If you don't need to monitor your performance logs, then you don't need this service.
Portable Media Serial Number - Retrieves the serial number of any portable music player connected to your computer
QOS RSVP - Provides network signaling and local traffic control setup functionality for QoS-aware programs and control applets.
Remote Desktop Help Session Manager - Manages and controls Remote Assistance. If you are not using Remote Desktop you don't need this service.
Remote Registry - Enables remote users to modify registry settings on this computer.
Routing & Remote Access - Offers routing services to businesses in local area and wide area network environments. Allows dial-in access.
Secondary Login - Enables starting processes under alternate credentials. This is what allows you to run an application as another user.
Smart Card - Manages access to smart cards read by this computer.
Smart Card Helper - Enables support for legacy non-plug and play smart-card readers used by this computer.
SSDP Discovery Service - Enables discovery of UPnP devices on your home network.
TCP/IP NetBIOS Helper - Enables support for NetBIOS over TCP/IP (NetBT) service and NetBIOS name resolution. This should not be needed in today's network environment.
Telnet - Enables a remote user to log on to this computer and run programs, and supports various TCP/IP Telnet clients.
Uninterruptible Power Supply Service - Manages an uninterruptible power supply (UPS) connected to the computer.
Universal Plug and Play Device Host - Provides support to host Universal Plug and Play devices
Upload Manager - Manages synchronous and asynchronous file transfers between clients and servers on the network.
Volume Shadow Copy Service - Manages and implements Volume Shadow Copies used for backup and other purposes.
Web Client - Enables Windows-based programs to create, access, and modify non-local files across the Internet.
Wireless Zero Configuration - Provides automatic configuration for the 802.11 adapters
WMI Performance Adapter - Provides performance library information from WMI HiPerf providers.