Updating HDX to v1.7b

Should be just fine.

Yes, in theory, it should be - the HDX is spec'd for CDRWs.  But the format of CDRW is different to CDR and I don't want to brick my HDX with an ISO that it may not completely recognize when loading firmware.  Has anybody used a CDRW to update the HFX?

I thought about it but opted for a CDR in the end, just in case.

A bit wasteful I know...

With a new version of firmware out about every 24 months maybe a bit less, I find it better to use a fewcdr disks to be sure. Actually I do not  own that many cdrw disks anyway.

In the accompanying "readme" notes for the upgrade, Naim advise against using CDRWs

Even the utterly rip off maplin charge like a fiver for 50 cdrs.

Yep, just scoured the accompanying installation guide and, sure enough, it advises against CDRWs.  Would probably work fine but I guess if it's an old CDRW with loads of writes and erases, it could bung up the works.  Dang, another 10 cents down the crapper!