It could be a faulty CDR he's trying.

Have you tried several different discs?

When you get your problems solved also remember that if you're sending a cd it should be checked it for errors.
I 've kept my older Plextor + plextools especially for this to check for c1 / c2 errors before sending any cd off. 
Use good quality disks (i.e. Taiyo Yuden) 

...& don't use sharpies on them either!

I don't think it's a faulty CD, I've tried two different Taiyo Yuden gold discs - no recognition of drive.

No, not a disk problem if the player isn't getting recognized. 
I'd re install / update your drivers. Also IIRC iTunes & anti-virus software has caused problems for some in the past.

Thanks. I did reinstall the software. No change.

Someone suggested that I make a DDP file - would this work? If so, how is it done?  

Can you burn ANYTHING?

Have you tried burning something from Windows Media Player?

Of all the components within a pc, I've had more optical drives fail on me than anything else.

The fact that 2 appear to have failed bends probability laws somewhat, but you need to eliminate the obvious, one step at a time.

Thank you. Yes, everything is burning normally - audio, data, images, etc. no problem, on both PCs.

It's just that CD Architect cannot find a writer/drive and I have no other software that can burn a Red Book master.

Snookered methinks.  

That is strange.

You might have to uninstall CDA & start again.

Reading through the CDA change logs, it's clear that it has a long history of failing to detect specific drive types. Apparently, there is an internal database of supported drives that CDA references to find out what your drive's capabilities are. If your drive isn't on the list, CDA ignores it. Over the years they've continually added to the list, but it's bound to be out of date as soon as a new revision is released - seems like a very 1980's-era approach.

There is an option in the CDA Preferences labeled "skip drive database, autodetect drive capabilities on startup". You might give that a go and see what happens.

That sounds like a good idea! Off to try it now.  :)