Try GetTickCount: – You can use this to tell how long the computer has been running – From there you can calculate when the last reboot happened.

http://msdn.microsoft.com/library/en-us/sysinfo/base/gettickcount.asp

GetTickCount(),Long,PASCAL,proc,NAME('GetTickCount'),Dll(dll_mode)

local               group, pre(loc)
UpTime                long
UpDays                long
UpHours               long
UpMins                long
                    end


    loc:UpTime = GetTickCount()
    loc:UpDays = (((loc:UpTime / 1000) / 60) / 60) / 24
    loc:UpHours = (((loc:UpTime / 1000) / 60) / 60) % 24
    loc:UpMins = (((loc:UpTime / 1000) / 60) % 60)

Can display something like this:

 ' Up_Time = ' & loc:UpDays & 'd ' & loc:UpHours & 'h ' & format(loc:UpMins, @N02) & 'm'

Cheers
Jono Woodhouse