I was in outlook 2007. My Vista computer rebooted automatically
Hmmm.. I haven't heard of Outlook crashing the entire system by itself. Are you sure there wasn't a blue screen? Perhaps it went by too fast for you to see the error, but (all versions of) Windows restart on a blue screen. If it's only very occasionally, this behavior is probably fine. AFter all, most users woudl simply return to whatever they were doing, say bad things about Microsoft, and go on about their day. But if/when you want to see what happened so you can look further, it's a little annoying since there's no time to catch the error code.
So - Click the Start orb, and in the search box type System - that will bring up your system tools. Run it.
On the left side - In the task pane on the left, click the Advanced system settings link.
Locate the Startup and Recovery area and click on the Settings button.
In the Startup and Recovery window, locate and uncheck the check box next to Automatically restart.
Click OK.. OK.. etc...
From now on, when a problem causes a BSOD or another major error that halts the system, the PC will not automatically reboot. Now you will have time to Groan, get a pen and paper so you can write down the error, and then manually restart.
That error is going to be important, since it tells us where to start looking.