I've seen this in the context of HAL replacement. But the same can happen in a number of different situations.
The general symptom is: even though your image already has all the right files on board, mini-setup halts and prompts you for the Windows XP installation media. When you browse to the system32 (or system32\drivers) folder, mini-setup is happy with the file that's already there and continues.
The problem seems to be caused by the absence of c:\windows\driver cache\i386\sp3.cab (that's for a Windows XP SP3 system - for SP2, it would be sp2.cab). If you update a pre-SP3 system by applying SP3, you will have an sp3.cab. But if your master system was built from a Windows XP CD with SP3 slipstreamed in, there is no sp3.cab.
Any time mini-setup (or more generally, the PnP system) discovers a new device for which Windows XP provides an out-of-the-box driver, the OS looks for the driver in sp3.cab, even if the driver is already installed. I suppose that even insignificant hardware differences between the source machine and the target machine, such as keyboard or mouse being in a different USB port, might cause mini-setup to look for sp3.cab, even though a perfectly up-to-date copy of the file it's looking for is already installed.
Solution: make sure your image has an sp3.cab (or sp2.cab in the case of sp2) in c:\windows\driver cache\i386. If it's not there, you can copy it from an expanded copy of SP3 and inject it during the post-imaging phase of your OSD script / provisioning template.