You can improve performance of your Windows XP and reclaim memory by simply disabling the services that is also known as "System Services" you don't need which Windows 2000 or XP automatically provide by default.

What Are System Services in the 1st place?

System services are actually small helper programs that provide support for other larger programs in Windows XP. Many of the services are set up to run automatically each time you start Windows XP. However, if you're not using the larger programs that these services are designed to support, these services are simply wasting RAM that could be put to better use by your applications. While the word "Disable" is used here to describe the idea that you'll remove these services from memory, what you'll really be doing is changing the startup setting from Automatic to Manual. When you do, the services won't automatically start each time you launch Windows XP Professional. However, Windows XP will be able to manually start the services if they're needed. That way you won't be unnecessarily wasting RAM, but you won't be crippling your system either.

Note: If you're running Windows XP Professional on a corporate network, you may not be able to adjust system services. Regardless of whether you can or not, you should check with your system administrator before attempting the make these changes.

Changing the startup type of a service from Automatic to Manual is a relatively simple operation. To begin, open the Control Panel, open the Administrative Tools folder, and then double click the Services tool. When you see the Services window, set the View to Detail if it isn't already. Then click the Startup Type column header to sort the services by Startup Type. When you do, all the Services that start automatically will appear at the top of the list.

As you scan through the list of services on your system whose Startup Type setting is set to Automatic, look for the services in listed in the Table below. These are some of the services are good candidates to be set to a Manual Startup Type.

Examples of services that can be safely changed to Manual :-

DHCP Client -- You're not connecting to a specific DHCP server on your local network
Distributed Link Tracking Client -- You're not connected to a Windows 2000 domain
DNS Client -- You're not connecting to a specific DNS server on your local network
FTP Publishing Service -- You don't need your system to act as an FTP server
IIS Admin Service -- You don't need your system to act as an WWW server
IPSEC Policy Agent -- You're not connected to a Windows XP domain
Messenger -- You're not connected to a Windows 2000 domain
Remote Registry Service -- You don't remotely access the Registry of other systems on your local network
RIP Service -- You don't need your system to act as a router
Run As Service -- You don't use any applications that run as an alias
World Wide Web Publishing Service
You don't need your system to act as an WWW server
If you find a match and think that your system doesn't need that particular service, right-click on the service and choose the Properties command from the shortcut menu. When you see the Properties dialog box for that service, click the Startup Type drop down list and select Manual. Then click OK. As you change the Startup Type for any service, take note of the service's name. That way you'll have a record of which services you changed and can change them back if you need to, as I'll explain in a moment.

Using the Windows Task Manager
Trick : To determine the amount of RAM you'll regain by disabling unnecessary system services, use the Windows Task Manager. Here's how: Before you disable any system services, reboot your system and don't launch any applications. If you have applications that automatically load when you start Windows, hold down the [Shift] key to bypass the Startup folder. Then, right click on the task bar and select Task Manager from the shortcut menu. When you see the Windows Task Manager dialog box, select the Performance tab. Now take note of the Available value in the Physical Memory panel. After you disable those system services you deem unnecessary, reboot your system in the same manner and compare the Available value in the Physical Memory panel to the one that you noted earlier.

Final thoughts about Windows XP Speed Up
Keep in mind that you may not find all the services listed in the Table set to Automatic on your system. In fact, you might not even see some of the services listed present on your system. If that's the case, don't worry about it. Each Windows 2000/XP installation is unique depending on the system and installed software, and different sets of services may be installed and set to start automatically.

On the other hand, you may find services other than those listed in Table set to Automatic that you may think are unnecessary. If so, you can find out what each service does by hovering your mouse pointer over the service's description. When you do, a tool tip window will pop up and display the entire description of the service. You can then better determine if the service is unnecessary. Remember, by changing the Startup Type to Manual, Windows XP can still start the service if it's needed. If you decide to experiment with changing the Startup Types of certain services, you can monitor the services over time by launching the Services utility and checking the list of running services. If you consistently find one of the services you set to Manual running, you may decide to change the Startup Type back to Automatic