To easily figure out when your machine was last rebooted, open a command prompt and enter
net statistics workstation | more
The second line of text will display
Statistics since...
The date and time that displays are when the machine was last started. To find the same information on a server, enter
net statistics server | more
This information comes from the workstation service and the server service.
—Tim Fenner
jedifenner@netscape.net