My rigs main H/D died over the weekend. During the rebuild i seemed to have lost the product key for my legit XP Home, so i used my cough iffy copy of XP Pro.
Having found the code for the genuine copy after reinstalling everything, is it possible to get this changed over to XP Home on the correct key, without re-registering or losing the install?
Also, the new drive has previously been a backup and is 250gig under XP Home, the XP Pro only sees it as 128gig.
:wall:
I once tried to install XP home using a Pro CD and home key, but it refused to accept it.
Bad news, your in for a re-install 
Allthough there’s not staggering ammounts of difference between Home & Pro, they are not the same. It’s possibe to ‘upgrade’ from home to pro but there is no way to downgrade afaik, sorry.
small spherical objects
[QUOTE=Walter O’Reilly;370052]Also, the new drive has previously been a backup and is 250gig under XP Home, the XP Pro only sees it as 128gig.
:wall:[/QUOTE]
XP has to have service pack 1 installed to see HDD larger than 130gig I believe.
If you want to install a service pack, it will know certain codes are not legitimate and refuse to install, but lots of newer bent keys still work.
Even when you install service packs 1 or 2, windows update will then download the WGA update checker to your PC, and it will annoy you everytime you start windows: A quick look through Google would bring-up a tool to remove this though.
Best way is to choose which updates to install, and not install it.
There is another workaround to the HDD issue. Open regedit and navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Atapi\Parameters. Create a new dword key called EnableBigLba and set it to a value of 1. Should see the full drive on a reboot.