You'll need to send a magic packet (For Wake ON LAN) through your router. Difficult because router's don't forward these by default, but there are workarounds as found here:
In order to wake up a computer from
the Internet you need a Broadband
connection with a Router connected to
the Modem that keeps your connection
alive (you need a Router even if you
have Static IP).
Waking Up the computer from remote is
done by sending the magic packet
through the Internet using your
Internet IP address, and the MAC
number of the computer that you intend
to Wake Up.
If you do not know your IP address:
Link to: How I find my Computer/Server
Internet address from remote location.
You have to prepare the system for
Wake Up Over the Internet.
Open a Port thought the Router, and
the Software Firewall (use high port
number so it will not conflict with
any other port, 5850 is a good
example).
Assign the port to the internal IP of
the computer that you want to WOL (you
can use the port only for one
computer).
Get this Utility it let you define a
port for WOL.
Link to: Wake on LAN for Windows
Graphical User Interface (WOL GUI)
Take with you a copy of the WOL GUI,
and write down the MAC number. In the
remote location start WOL GUI and type
in your MAC number, Type in the
Internet address (Internet IP) type in
the port number that you left Open.
Click on Wake me Up and it should
work.
The utility:
The magic packet GUI utility is freeware.
You can also use a hotkey to wake it along with the command line version of Wake On LAN:
The Syntax:
C:\path\to\wolcmd.exe [Mac address] [IP address] [Subnet mask] [port number]
Making things easier:
!w::Run, C:\wolcmd.exe 009027a324fe 195.188.159.20 255.255.255.0 8900
- Alt + w will wake the remote computer
modify the script accordingly so the path points to the wolcmd.exe
executable and the MAC, IP, and subnet are correct.