Simcity4: Rush Hour expansion won't install

[Helevitia]

I tried a bunch of things already. If anyone has any ideas, please let me know. All of the info is posted in this thread:

http://www.simcitycentral.net/forums/viewtopic.php?t=9335

Thanks!
Dave

[Helevitia]

Somebody found a fix to my problem, but no explanation why.

I had to boot into safe mode and log into the admin account. Then install it. I tried booting into safe mode earlier and log in with my account, which has admin privileges. So why is the admin account different and why doesn't it work under XP normal?

Dave