Backup server + using it as a file server

I currently have in our house:
- 1 Desktop computer
- 1 Laptop computer

I use both of these for work so I need a solution where I can use the backup/file server to store all "work" files that I will need to be able to access from either computer and be able to leave the files on that server while opening/working on them.

Current setup:
Windows Home Server (2x500gb drives)
This images the computers on the network and allows me to backup/share files as needed. However I don't really like the fact that I can't hook up a monitor or use it like a normal computer to setup/configure the backup routines more easily.
Windows home server has had issues in the past about corrupted files if they are opened/worked on while still on the server, which bugs me.

Objectives:
- Backup/File server
- FTP/remote access
- Ability to setup a program like Syncback so I can FTP some important files to and off-site server from the backup server
- I like the idea what windows home server creates images of the hard drives in case they completely die

Questions
- Should I build a small server from scratch, put winXP on it and use it along side the home server?
- Should I ditch the windows home server and buy some disk imaging software and run it in the newly built backup server?
- Any suggestions/threads/articles on building a decent server like mentioned above?
- I have an old computer I could use but I am thinking building one that will always be on is going to be better to lower power consumption.