If you do not feel comfortable reinstalling Windows, there is a better way to move your new HD to the other computer. This requires moving the new HD back to the system from which the Windows XP and SP2 were installed. Boot the computer and replace the chipset controller with the standard IDE controller.
From Device Manager, right click on the chipset IDE controller and Update driver > Install from a list or specific location > Don?t search. I will choose the driver to install > Standard Dual Channel PCI IDE Controller.
And remove all chipset devices from System Devices. Also remove all devices (Network Adaptors, audio, video, and so on).
Move the HD back to the other computer as the Primary Master. The Windows will find all the drivers it can. You need to install the MB drivers and others if necessary. All your programs and data should be intact. SP2 will be there too including all MS hotfixes and updates.
If this fails, then reinstall Windows.