How i fixed a DH20A4P A drive not reading DVDs

i too ran into the problem of the DH-20A4P suddenly not seeing DVDs anymore
I ruled out any OS problems
it would not see DVDs to boot from

using the LtnRPC.exe tool i reset the region to 0 (user and device)
then reset to 1

now it sees dvds (video and data) in win enviro. also it will now boot from DVDs

(and i was about to order a replacement!!)

hope this helps someone else

Thanks. Had you loaded the drive with any kind of non-standard firmware before?