How do you mean by copy stuff to the disc? Unless using some sort of packet writing softwear, In-CD for example you cant just copy stuff over, that is the area of DVD-RAM. You need to use a burning application like Nero or Roxio to burn data onto the disc. I am not trying to be picky but it helps us to try and find the problem.
Therefore we need a lot more information to help:
Make and model of drive (should be listed in the burning app itself)
The steps you are following before you get the error message
Whether you have tried different software (Nero for example) and if the same problem arises
Does the media work in another PC, a test you already know about,
Does the drive recognise and work with different media
If possible the MID of the discs (download Nero CD-DVD speed and the information will be in the disc info tab you should see a line with letters and number for example TYG03, G05, MCC004 etc)
What are you trying to burn (no need to be specific iso, backing up a DVD, data for back up)
I am sure others can think of more tbut this will get us started.