Windows 7 - DVD RW drive wont detect blank dvd's

Hi i am having problems with my dvd drives they will both read discs with data on but wont detect blank media, i have tried a number of things now, ive uninstalled them, ive removed the filters in the reg, ive searched for firmware updates and ive tried restoring my system, its not the media either, any i try is the same and they are fine in a different system, the only thing i can think of is if something happened when i changed from xp to 7 but im sure ive burned dvd whilst running 7 before, cant remember. The drives are SONY DVD RW DW-D22A and LITE-ON COMBO SOHC-4836K.
Any help is appreciated.
thank you.

Hi s3amus,

Try this:

Right Click My Computer and select Manage. Right click on the Blank Disk and select Format, unselect Quick Format and Proceed.

Then Autoplay should also to rename the CD and chose if you want it to be like a USB or Burn Once, or you may have to do it manually if AutoPlay is Disabled.

Hope this helps

just checked the computer management the blank disc doesnt even show up, its as if the drives are empty.

Have you got the most up-to-date drivers, are the drives faulty?

drivers are fine and up to date, my computer is pretty old and designed for xp, would running 7 have anything to do with it?