Upgrading from 5 to 6 crashes on install

Hi There,
I've been running Parallels 5 on my 3 year old Macbook Pro. I just migrated to a new i7 2.2 ghz Quad Core with 8 gigs of ram.
Then I bought Parallels 6 through Macupdate spring bundle, and began the install (thinking it would just upgrade over the old install).
The version is Parallels 6.0.11994.637263
I clicked on the app and it continually crashes as it's configuring. I get a message:

You need to log in to Windows to complete configuring your virtual machine.
If autorun is disabled, you will also need to open My Computer and run the Setup.exe file located on the CD, ignoring any Windows notifications. For more information, visit Parallels website.

First of all, how can I log into Windows if I can't even run it?

This message is right over top of a blue screen of death saying:
A problem has been detected and your windows has shut down to prevent damage to your computer.
etc...

I've tried installing 4 times and it hangs the same way.

After reading a bit, I'm trying to figure out if there is a way I can downgrade back to version 5?
It seems like I can't go forward so I need to go back. I have my old registration code for version 5, but where to download it? And how to uninstall this current version 6?

Help!