Here's a quick way
To find out last reboot
1) Open command prompt and type in
net statistics workstation | more
The second line will say
Statistics since ....
You can find out since when the machine is up
To Find out last shutdown
The easiest way to determine the last shutdown date/time is to check the event logs. When you shutdown a computer Event ID 6006 is written to the Event log which denotes a clean shutdown.
Enjoy...
