windows 7 64 bit freezes shortly after start up

I have windows 7 Ultimate - 64 bit operating system that freezes shortly after startup -- works in safe mode. I have only used this system as the administrator. If I select another user besides administrator, it seems to work fine.
The problem started a couple weeks ago while I was using outlook 2007 in reply to a new email from a commercial vendor. Outlook hung up while I was replying or looking at an email from this vendor. I had to do a hard shut down of the system to get out of Outlook as the system was non responsive. That is when the freezing problem started. When I rebooted the system, the system froze shortly after startup (sometimes a minute to 3 minutes of use after startup).
I attempted to recover the system to an earlier date but as I was doing that the system froze and wiped out all of my earlier recovery dates.
I have learned that if I use a secondary user, the system does not hang up, or freeze. I have not attempted to use Outlook as a user because I did not want to corrupt that if Outlook is the problem. I also find that I cant access many of my files in user mode as the system tells me I have to be an administrator.
How do I determine where the problem is?
Some other considerations- I sent my wife an email from Outlook from my corrupt Outlook / system and her Outlook in MAC OS told her that there could be a problem with Outlook -- gave her an error that Outlook was experiencing a problem.
Please advise.
Thank you.
Pontiac Power