The Online Tech Tips site offers up a great tip for anyone reinstalling XP off something other than their original CD—such as a slipstreamed and automated installation—or lacking a net connection to run the activation. Before wiping your system clean, grab a file named
WPA.DBL from the System32 directory and save it to a thumb drive or other external media. When you load up your new system, skip registration, enter "Safe Mode" from the boot menu, and drop it back into that System32 folder. Now you're re-activated and free of nagging. Hit the link below for detailed explanation of each step.