The eternal question.

Multitracking on a computer used to be so simple it seemed- protools was king, then there was cakewalk products if you did PC.  Cubase was next on the block.

If you have an old machine I would suggest older hardware and OS's.

The best luck I've had were the motu products.  I have a 4 year old machine running windows 2000 OS.  What I'm going to do is just upgrade my studio with another 24 bit Motu 828 version 1- these only have a 48K sampling rate, but they are pretty solid if you run the audio desk hardware they come bundled with- you have to have a mac to run audio desk though.  Unfortunately you have to get a used mac still running OS9.

So then I can keep my loud as heck hot rodded studio PC *overclocked with multiple fans* and hot CRT monitors.  Between that and the tube gear my air conditioner is always kicking on during a session- not the coolest thing in the world if you really want super hi fidelity.  But it's a project studio, so whatever.

I have to say that "sonar" from cakewalk is a very easy to use program that is pretty solid.  As long as the thing will run on your older boxes and has drivers for your hardware interface/audio input then you will be ok.  That's the trick though.

For my recording, I bought a decent 16 channel mixer and bought a converter for 1/4" stereo out to 1/8" stereo in so I could plug into my sound card. I can hook whatever I want into the mixer, set the individual levels, and then adjust the mixer output to something the computer likes. Almost any soundcard does 44.1 kHz stereo (cd quality) these days so as long as you adjust the recording level to the maximum without clipping then you should get very good quality recordings with low noise.
Try to keep the computer monitor away from mics and instruments because it will add a lot of noise to the recording.

I use either Win98 or WinXP with a soundblaster sound card (44.1kHz stereo) using a shareware wave editor called CoolEdit Pro. One machine is 1.2 GHz, the other is 2.0 GHz. Sound recordings can be pretty large so I'd suggest having at least 20GB available. I bought a DVD burner so I could move older recordings off the hard drive.

The sound you record will obviously be affected by your microphones and the room you record in. Although you may be recording cd quality it may not always sound good overall and this has been my biggest problem so far.

My thoughts from having used this setup are:

1. Get a fast hard drive (7200 or 10000 rpm) with a large cache. If the disk can't write fast enough while you're recording then your recording will have some skips in it and will generally be useless.

2. Anything you plug into the mixer will be recorded as a single track so if you want instruments on separate tracks (to allow later mixing) then you need to make 2 recordings. This is where it gets tough because all tracks need to be synced which requires either playing with a click track or recording all the drums first and recording everything while listening to that track.

3. Get a good wave editor. I use a shareware program called CoolEdit ($29), but I think it was bought by Adode so it may have been renamed. Audacity is a good freeware editor. All tracks are recorded by the wave editor. Once recorded you can save the file in any format you'd like (make sure it's not a lossy format like mp3).  The nice thing about CoolEdit is that it has a simple mixer built in so you can sync everything, adjust the levels, and export to a single file easily (no individual channel effects though...).

4. Since instruments are recorded separately you don't get the same mix of sound as when you record live. You don't get the sound interaction of the bass with the guitar with the drums with the vocals, etc. Overall, I don't think the sound is as vibrant and sounds overly produced, but it works great for laying down tracks to practice with or trying out how different parts sound or just recording new ideas for bandmates to listen to.