What you're looking for is Windows Home Server. It's amazing. Stores all the media you need, plus has streaming capabilities over the net. Able to expand perpetually -- no need to reformat or anything like that. I have it running with 10TB of space. It has a great front-end UI, and as close to zeroconf as you can get with this type of service. See exampel screenshot: http://ivivo.files.wordpress.com/2008/09/windowsho…
I know WHS is probably easier to set up, but Microsoft did not pioneer the concept of "drive extender". Linux had something called LVM since 1998. According to Wikipedia, IBM AIX had a similar feature in 1989. MS also had similar capabilities in NT for quite some time now (disk volume sets), they just weren't shown to the home users. Autobackup can be done by rsync, file access by Samba, printing through CUPS. Oh yea…
RE: concept, understood it may be used for other OS's. Was pointing out that WHS uses a different file system than normal windows, one built to scale in terms of drives.