Login across the Internet

My server has an internet-know IP address(not 10.x.x.x or 192.168.x.x). How can I login to NT from my house or a branch office across the internet without special software? We would rather not use a VPN or PPTP. I also know that you can map a drive across the internet but I need to know how. It is a path context or some other format? We want to be able to do this as simple as possible, i.e. using “net use” commands or built in funtions.