Fatal error during upgrade to SCCM SP1

First of all check the configmgrsetup.log file.

If SCCM and WAIK are not installed on the OS driver (another partition)

and you receive 1603 error during the Waik Installation, this is the reason:


During the ConfigMgr 2007 SP1 upgrade process:
WAIK was uninstalled automatically
WAIK was attempted to automatically install using default settings.When the upgrade attempted to reinstall the WAIK it defaulted installed to the default OS drive. This failed on my server.

Solution

Before attempting to run SP1
Uninstall WAIK via ARP (Add Remove Programs) (if the previous attempt of SP1 hasn't done it for you)
Install WAIK via the new copy in: . \SCConfigMgr07_UPD_EN\SMSSETUP\WAIK\
Run the SCCM SP1 upgrade again