[Neil H]

My advice ditch them asap/sell them on asap if you are not already deep into ownership of an HD rig it will be a money pit with very little if any returns on the investment.

There are many good reasons why you got these cards cheap.

HD TDM is old outdated and under powered compared to whats out there on a native system.
Even if you built an incredibly powerful computer to use the cards with you would not be able to take full advantage of the computers native power because the HD cards will be a restricting factor as they will max out of voices first.

First you need a computer with native PCI slot bus support which ended some years ago now on most boards I think the only to still support it are intel B series and then you need enough PCI bandwidth to handle the cards all running at once which was a huge headache when trying to build systems for TDM use, boards with such features are hard to find if not now impossible.

Then you'll have to be running 32 bit Pro Tools and the latest version you can use is PT10 (this has to be PTHD10 not just regular native PT10 and is very expensive compared to the native version) 32bit Pro tools has a RAM limitation where it can only take advantage of a maximum 3.5GB of RAM even if you full your machine with 64GB. 3.5GB is a very small amount these days and will get eaten up very quickly with plugins and don't even think about virtual instruments!
Then there's the plugins, To take advantage of the TDM DSP chips you'll need HD TDM plugins not native, although native will work with Pro Tools you'll soon eat up your voice count bussing back and forth to native plugins and you can'y real time monitor though them on record without a TDM plugin inserted in the first slot.

If you cant find a board with enough slots and PCI bandwidth your next port of call would be a Magma expansion chassis such as P7R4 or PE6R4i which again is more investment (will cost a few hundred) Or you can buy an OLD G5 Mac that had PCI slots and will be a slow as a snail that's just been squashed.

Then you'll need an interface such as a 192io or a 96io (another few hundred) to get the audio in and out.

If not much of what I'm saying is making sense to you then you have a lot of learning ahead of you so stop right there and get rid of the cards and try to make your money back, or you can of course ignore me and prepare yourself for spending a lot of money on a lot of headaches for no more gains but quite a few more limitations to a regular Native CPU rig.

I've had several TDM systems over the years and still have one in my studio but only because i'm heavily invested in 5x cards in a magma chassis lots of TDM plugins, 4x interfaces, a Pro Control and 2 fader packs so do have plenty of experience.

If you are still dead set on using them and i haven't put you off yet, You could look for a used HPXW8400 PC which will take the cards, Run Windows 7 and Pro Tools HD 8,9 or 10 and I wish you the best of luck !