What OS are you running?

[Addict]

Services that can be disabled
Application Layer Gateway Service
Automatic Updates
ClipBook
DHCP Client (be sure you are using a static IP address)
Human Interface Device Access
Internet Connection Firewall (be sure you have another means to prevent unauthorized access prior)
Routing & Remote Access
Wireless Zero Configuration
Messenger (this will also help to prevent the 'new' spam messages, but will prevent you from using net send command)

Other tips...
-Set the theme to Windows Classic. This will remove all the pretty buttons & such.
-Turn off Font Smoothing (Display Properties->Appearance->Effects->"Use the following method to smooth edges of screen fonts"(uncheck the box)
-In the same place, uncheck "Show shadows under menus"
-Turn your monitor refresh rate up to as high as your monitor will allow. Please check you manual prior. You can seriously damage the monitor with the wrong refresh rate. Most monitors can do 72Hz with no problems. XP's default is 60Hz.

That's all I can think of for now.