Ok,
The delay in startup maybe related to the service thats failing - which service is failing (ie open the event 7000's and it will tell you which service failed to start).
One of the DCOM errors appears to be related to DCOM permissions! Might be worth running the 'Set Program Access & Defaults' wizard in case something has messed up the permissions in the Windows directory.
If all that doesn't do any good, you could try uninstalling that new driver and trying the earliest driver that supports the 7800 GTX (
http://www.nvidia.com/object/winxp_2k_77.72.html).
HTH