Hi addyali, have you done all the windows 7 system updates as well as all the updates from sony?
This may not solve your problem, but its at least worth a try. It could be that the dvd/combo drive requires the correct drivers to be installed before it can operate properly.
Do all windows updates and all sony updates for your laptop model and the see if problem is still their.
Good luck and lets us know how you get on :-0