To disable a service first open the services window at 'computer management/services and applications/services.'

Highlight the service you wish to change, right click and select 'properties.' Hit the 'stop' button to stop the service, then set the 'startup type' dropdown box to 'disabled.'

This stops the service and ensures that it will not reload upon restarting the computer.

Local security policies (XP professional only)

Accessed through the 'administrative tools' menu found in the control panel, the local security policies window controls the various XP security options like auditing (keeping a log of which users log into the computer, and what resources they access.), password complexity requirements, what users are allowed to log into the computer remotely, etc.

All important stuff, but generally something that is useful more at the enterprise level than for individual home users. If your PC is used by several people, or if you have had problems in the past with someone breaking into your PC, you might want to consider some of these settings.

Going through the groups, 'account policies' governs password settings like minimum length and complexity requirements of user passwords, and whether there is a limit to the amount of times they can be tried before the account is disabled for a period of time.

The 'local policies' section contains auditing options, which when set will add reports to the 'security' log in the event log section of the computer management window, so you can see who is accessing the resources you have audited.

All auditing is disabled by default, and generally speaking if you wish to enable it, limit it to one or two options, like auditing account logon events, not the whole bunch, or you will be overwhelmed with pointless log entries.