See if this Microsoft Article is helpful ..........

http://support.microsoft.com/default.aspx?scid=kb;en-us;316529

Thank you, Skybird,  for the information: I did follow the proposed procedure, but for both devices the appropriate keys were set to 'write-enabled (Drive Type value = 2) but the DVD property-windows of the individual DVD-drives show under Geräte-Typ: 'DVD/CD-ROM-Laufwerke'.

Thus - no success, sorry

Will the drives write to DVDs?  They show as DVD-ROM in Windows XP because XP cannot write to DVD media.  Thus, third-party software is required to write DVDs.  Windows XP will only recognize a DVD Writer as a DVD-ROM.

Hi Skybird,

thank you very much for your response and the very valuable information about Windows-XP and its DVD capability.
in earlier days I could write to DVDs with NERO version 7 software, but since a few months NERO does not complete the writing process. Within NERO software both drives are recognized and identified as DVD-RW drives. On my second PC (with Windows-XP) I also have a DVD-RW drive and identical NERO software. There I can write to DVDs without any problems.

Any idea what's going wrong?

Thanks in advance

It looks like something is going on with Nero. 
I am not a Nero user.  What is the error you
are receiving with Nero when the writing process
fails?

High Skibyrd,

thanks for your hint - you are right, NERO software was damaged and I did reinstall my software. The most important issue was your info about Windows-XP DVD capabilities/restrictions. That was very helpfull for better understanding of Windows-XP.

Thanks so far and have a nice weekend

Yours Ernst Schubert

Glad you got things resolved.  Best regards.