DVD drive can read DVDs/CDs and can write CDs, but can't write DVDs

I have a Dell Dimension 2400 with an NEC ND-2100AD drive. I’ve spent some time today changing some things with the help of Dell support. After an hour or so, they said that the drive just doesn’t write to DVDs anymore. (It did once.) It reads from both DVDs and CDs and writes to CDs, but not DVDs. Would using the converter to convert the drive to a 2500 help at all or is it just dead?

That will not help if it doesn’t write to +R yet.

Test it in another computer first.