I got to my desk this morning, and one of my Windows 7 computers had rebooted overnight. This is usually caused by an automated update; Windows seems to think that after any change, it needs to reboot. Linux doesn't, unless it's the kernel.
I'd rather control reboots myself. If you need a reboot, tell me, but don't just do it.
So here's how you tell a Windows 7 box to do that.
Start -> search for gpedit.msc or search Run, select it, and then type gpedit.msc.
Now drill down as follows: Computer Configuration -> Administrative Templates -> Windows Components -> Windows Update.
Double click on "No auto-restart for scheduled Automatic Updates installations"