I bought a new W7 laptop last year and upgrade W7 disc for my upstairs PC.
The upstairs DVD packed up immediately.
Since it is also connected to an external USB DVDRW drive, I wasn't too worried.
And of course my laptop has a DVDRW drive.
Since then I have Googled occasionally.
Bit of a coincidence. upgrade from XP to W7 and the DVD packs up.
Vut I have now come to think the DVD laser has failed.
It still works as a CD drive.
You could try this utility, you may be lucky.