I wasn't going to bother upgrading to a media server powered by Vista, but the following ThinkRemote claim assumes that you've got it:
Change the music
from the kitchen. Check the weather with your
fridge magnet. Review stock performance by your
bedside. The possibilities are limitless, since
your PC is now a whole-home entertainment and
information hub.
Microsoft claims that you can do all of that without turning on your PC, but I think the reality is that your computer is either on all the time, or it turns itself on at timed intervals.
If my computer is going to be on all the time, I'll be needing a beefier firewall, a disk-less design (SDD), and DC power from a float-charged battery.
I've seen XP, Win2000, and 2003 Servers that stay up for months at a time (with automatic updates OFF, of course), but sooner or later a power outage will occur and take something out, and most HDDs have managed to toast themselves within 8 to 10 years. An integral part of a home should require no more maintenance than the kitchen plumbing.
