inputting new registration code

[Jimmy]

I reformatted my computer recently and installed Windows
XP Pro, but instead of putting the registration code for
XP pro I got mixed up and end up putting the registration
code for XP. The installation continued and ran without
a problem. Everything was fine until I was trying to
install the service pack for XP today. It said that my
registration code was invalid and that's when I realized
it. Is there anyway that I can change the registration
code without reinstalling the OP?

 

[Tony Cox]

Go to Start --> Run
Type 'regedit' and click ok
Expand HKEY_LOCAL_MACHINE folder
Expand SOFTWARE folder
Expand Microsoft
Expand Windows
Click on 'Current Version' (not expand, actually look at
this one)
There is a value there called 'ProductId' which I believe
is the key you originally put into windows although I'm
not certain. If it is the same as your 'old key' change
it to your new key, otherwise leave it alone as it will
be somewhere else. Have a browse through all the keys
and see if you can find it if this is the case.

 

[Michael Solomon \(MS-MVP Windows Shell/User\)]

XP In Place Upgrade To Change License Key
http://www.michaelstevenstech.com/xp_in_place_upgrade.htm