VNC: Unencrypted remote administration tool, generally used in network LAN settings where sniffing programs are not of much fear.
RDC: Encrypted remote administration tool, also used in network LAN settings, however requires a terminal services lisence to operate.
VPN Win: Requires that a machine be made available to the internet for outside requests. PPTP or L2TP as a server, I believe. I have never setup a Win VPN server myself.
Hardware VPN: Only requires making the hardware device available to the internet (for a device like a PIX, this is a given). Can support multiple VPN tunnel models, and many encryption and hashing algorithms. Provides better security, as you are not required to give a Windows machine a port directly to the internet.
Computer/Network Technician
CCNA