Due to an extremely long and boring saga, I'm going to have 1.75 computers. I'd like to take the extra parts I have and build a home file server. I'm concerned about two things. First, what's the best way to configure the system for reliability. (Is RAID worth it?) Second, what can I do to minimize the power consumption of hardware that was intended for desktop use?
Don't overclock and don't disable power saving features in the BIOS. Use a low-power fanless video card instead of a Radeon X1900GT. You don't really need RAID, but you could implement RAID 1. Regardless, if your data is important, it should be backed up on a regular basis.
The rest is fine, i.e., you could build a system that uses less power, but the savings aren't worth it if you need to spend more than the power savings over several years. Read the HD 3450 review and check the idle power requirements of their test system (your server will be idle most of the time).
Quite literally, go on ebay and get the cheapest graphics card you can. Servers don't need much power. I got a Radeon x300 for $7 shipped for my server. You could even sell the one you have.
If it'll be your backup place then getting a RAID 1 is pointless since you already have the stuff in two places. I'd say 1.5 terabyte drives are the best for the money. I'd say either the samsung or the WD for $109 if you need it.
Just get the cheapest case with free shipping on newegg that doesn't have "my hand was cut off" or "it collapsed" reviews. Unless you want to upgrade your actual computer's case and use your old one.