Depending on your preffered method, GUI or CMD-line.
You could use RDP of course, or a varriant of VNC, (tightVNC, UltraVNC, whatever) If you are remote (as in not in the same network) you can use a free VPN like
HamachiOtherwise, use PuTTY or some varriant (KiTTY) to SSH in to the box. Not sure what utilities people are using once SSH'd in though.