Alternatively, have you considered Windows Home Server? I've just built myself a fileserver using a K45 Shuttle with a 2ghz Celeron, 2gb ram and a spare 320gb barracuda. It's running whs (120 day trial), so before that runs out I plan to stick a 1tb WD Green in there and buy the full version.
Cost me £150 for the parts so far, plus ~£190 for the WD and full copy of whs in a few months time.
im interested in this too. Just got a copy of Windows Home Server and was wondering if you guys have ever experienced it.