There are probably a ton of tutorials out there online that I'm too lazy to
google at the moment.I would like to see other folks giving their
input here. I would love to build something like this...

In terms of cost vs features the ready built DVR's really can't be
beaten IMHO. The have dedicated hardware and mostly run Linux too but
a very stripped down and lean version. What these need is a fast HD
and no unnecessary services tying up the CPU - quite often hardware is
custom designed for the job with the OS in ROM for 'instant on'.

If you are thinking more of the challenge then go for it, but don't
expect it to be a simple job and get to grips with programming rather
than installing pre-built software

I broke down and did a google search.

http://www.google.com/linux?hl=en&q=building+a+linux+based+dvr&btnG=Search

The main thing I'd like to accomplish with a Linux based DVR is to capture
video into a format that I could convert to a DVD for things like concerts &
stuff I know I'd watch more than a few times.

The thing everyone needs to remember today is that the USA is now using
ATSC broadcasting.
Under this digital broadcasting you don't need to encode/decode the
stream from OTA broadcasting.
So with that in mind you don't need as much "horsepower" to build a dvr.
If you have any older hardware that will use the old NTSC like a vcr or
cable box and you want to capture that source then you will need an
capture card with a ntsc input.
If you want to use Directv/Dish Network then it gets a little more
complex but depends on what you would like to use as far as the output
from the reciever.
Most good capture cards have component and s-video inputs as well as 1
atsc and 1 ntsc input for ota/qam capturing.
You can acquire capture cards for just component input but most don't
have good capture quality that I have found.

Do a google search for HTPC or PVR and you will get alot of hits for
building a pvr but some are older and refer to the older ntsc format.
Under the new atsc the stream is already in mpeg format so your just
essentially copying the stream to your drive.
Under Linux there is MythTV and Freevo for frontend/backend pvr.
MythTV has pretty good documentation on there website.

I bought a Philips Home Theatre 2 box outfit which records onto an 80 GB
internal hard drive. It's not 1080 p but it looks good. After over 2 years
the drive is about 80% filled. I've transferred some things, like the
opening and closing of the Beijing Olympics, to DVD, but they are still on
the DVR.

Cost was $180, refurbished. Well worth the money!

There are several potential issues. Most likely, a 10-year-old computer will not
have enough memory for a modern OS, the CPU is too slow for 1080P playback, the
video adapter is weak.

A DVR will be on most of the time. A computer such as the Acer Aspire Revo R3610
draws less power than your 10-year-old PC, enough to pay for itself in a couple
of years. It's no powerhouse, but it's OK as a DVR, and has a decent graphics
adapter.

I spent a few hours trying to shoehorn one of the tiny Linux distros into a 1997
PC. At some point I realized the computer doesn't have an ethernet adapter, so
it would be completely useless without spending some money on it.

I am surprised at some of the comments you have received about buying DVR/PVRs.
We have not found any current-production units with ATSC tuners for quite a
while. When my last unit died, I decided to build one. In the end, however,
instead of building an HTPC, I decided to do my recording on my desktop.

Your first need is going to be a tuner. I strongly recommend the HomeRun
network-based tuner. In fact, we are strongly considering getting a second one
so we have the option of recording or watching live OTA TV on four channels.

For your application, I think MythTV and MythArchive will meet your needs quite
well. MythBuntu is a pre-packaged release with Ubuntu and MythTV ready to go.
That said, I have not had any luck getting other MythTV frontends on the network
to pull from the backend on my desktop.

I have not tried burning shows to DVD, but MythArchive appears to be the app for
that.

This sounds like a fun project except for the antique computer. You will turn a
fun project into a miserable trial. You can get a new main board and case for
next to nothing now or even a new computer. You then can work to your heart's
content with doing a great home project. Don't torture yourself for the sake of
reusing a piece of equipment that should be in e-waste.

wanting to do it right the first time, thanks to everyone on their many
great tips and input but don't stop now, all information is appreciated.

Ed, looking at the SiliconDust HDHomeRun tuners the one I believe I need is
the HDHR3-US at this link
www.silicondust.com/products/models/hdhr3-us/

What do you have/recommend?

this is the unit I have:
www.newegg.com/.../....aspx It appears
to be discontinued, but you might keep an eye on eBay.

If you are willing to experiment, you might as well go ahead and try the
hardware you have with Mythbuntu. If it doesn't work, as others have said it
doesn't cost that much to pick up a motherboard, RAM, and a processor.