Installation Reboot Loop

[etheth]

This is very frustrating. I just bought Vista Ultimate to get to the final step in the installation. Now it just sits at a blank screen for about 10 minutes and reboots. I am on a Dell XPS 700 with about 4gb of ram, and a pentium dual core processor 3.00GHz. I can't log into safe mode without getting

"reboot into normal mode to complete the installation".

So what DO I do? BTW I upgraded from media center SP2.

 

[etheth]

Please, someone help me.

 

[Rich-M]

Did you add ram to this unit?

 

[etheth]

No, I haven't changed my computer before I did this.

 

[Rich-M]

OK so the 4 gig of ram came from Dell with the unit?