During the installation of Service Pack 2 on Windows XP machine process stops on Checking Product Key.
If you like me didn’t put the key in this can be less of a surprise but still.
To continue the installation:
1. Navigate to C:\Windows\Inf (Folder is not visible by default)
2. Move all oem*.* files to your desktop (or folder on your desktop)
3. Move infcache.1 to the same location
5. Finish the installation
I would keep the backed up files just in case but it seems that windows (or SP2) created new files in place of the removed ones.
Hopefully this will save you some time.