This was from a Microsoft website, but I modified for home and pro
users.

This will only work if your version of xp is LEGAL and 30 days have
not passed. Still might work even if the 30 days have passed if you
have xp sp1 or greater.

Click Start, and then click Run.
In the Open box, type regedit, and then click OK.
In the left pane, locate and then click the following registry key:
HKEY_LOCAL_MACHINE\Software\Microsoft\WindowsNT\Cu rrent
Version\WPAEvents

In the right pane, right-click OOBETimer, and then click Modify.
Change at least one digit of this value to deactivate Windows.

Click Start, and then click Run.
In the Open box, type the following command, and then click OK.
%systemroot%\system32\oobe\msoobe.exe /a

Click Yes, I want to telephone a customer service representative to
activate Windows, and then click Next. Click Change Product key.
Type the same product key you use to install windows xp in the New key
boxes, and then click Update. If you are returned to the previous
window, click Remind me later, and then restart the computer

Activate Windows.
Restart Computer
Check to see if windows is activated
Click Start, and then click Run.
In the Open box, type the following command, and then click OK.
%systemroot%\system32\oobe\msoobe.exe /a
Click OK.

Xp Oem preinstalled systems may not activate. So repeat above, then
use the product key on the back of your system instead. Then
Activate.

Greg R
Excerpts were from this page but modified for the home & pro users
http://support.microsoft.com/defaul…kb;en-us;328874

The reason I posted this new thread
I getting tired of people saying go out any buy a legal version of xp.
When they may have a legal version to begin with. Just the
activation Scheme got messed up by a bad install. Also, I getting
tired of people saying you need to reinstall. You shouldn