BB, It all depends on the age of your target computer. If it uses ATX pwr and will shut down completely from Windows when you use Start =>Shutdown then use a VNC program to connect to it and remotely shut it down.
I use
UltraVnc WIth this you can connect through a dedicated viewer or a Java enabled browser and do pretty much anything you could do if you had a mouse/KB attached.
If on the other hand your 'puter is the old AT pwr and needs a physical power off then you are stuck with it. You could still use UltraVNC to issue the shutdown cmd to avoid the "brute force" shutdown method. but the hand/button interface would still be needed.
Hope this helps
Max
Edit ...PiperPa ...posted the same info at the same time