Requirements for my home server?

Hello all, lately i have been looking into servers and home automation and media servers and stuff like that, and ive been wanting to set up one of my own for my home personal use. However the computer i am thinking about setting up the server on is a little bit old, i don't have the specifics at the moment but i think a 1.6 ghz dual processor with 512 mb of ram (possibly 1 gb). So i was wondering if it is possible to do all of the following tasks on this computer, if not all of the tasks then maybe just a select few. Here is what i want to do:

VPN/FTP/FTPS/SSH server

Home file server

Computer backup (not really important, i have 2 laptops on my network as well)

Home Automation (not important, however if it can be done thats great)

Media Server for streaming to my laptops and TVs...using Roku for my TVs (very important for me)

Managing an Active Directory for my laptops for a learning experience

DVR/PVR for TV

Downloading Torrents to server from laptops

I realize this is a large task load for such a mediocre computer, however these are just the ideas that i would like to try and if its possible for me to not go buy another fancy computer that would be great. I will be using a couple 2 TB harddrives for these tasks so space is not a problem.

So, is this possible? Thank you in advance for all help!

My main concern is the media server, as i believe this will most likely be the most intensive...but if i can do any of these please let me know which ones i can and cannot do based on the limits of my computer. Thanks!