1. Enabling Remote Desktop in Windows XP
Start > Settings > Control Panel > System > Remote (tab) > select “Allow users to connect remotely to this computer”
http://www.microsoft.com/windowsxp/using/mobility/getstarted/enableremote.mspx
2. Connect to another Windows XP computer using remote desktop
http://www.microsoft.com/windowsxp/using/mobility/getstarted/remoteintro.mspx
However, I would say that it should be done only when you are ready to allow remote connection; for instance; asking your friend to help solve an issue that s/he knows. Otherwise, it is best left deselected at all time.
Anyway, after recently converting to the Mac, I know I’ll never go back to Windows.
http://www.brajeshwar.com/archives/2006/07/mac-convert-am-i/