DVD disc damaged after 'Burn' being unsuccessful in Nero 7.

Hi! My name is Apoorva. I have faced a problem with my blank DVD.

I had burned a blank DVD (Morserbaer ) in the month of July with some Data files using Nero 7.

Than, I kept this burned DVD into the "DVD Pack" which is provided by Moserbaer when one purchases a
10 Pack DVD.

Today, few mins back, I had inserted the same DVD into the DVD writer ( Liteon ) inorder to burn few more data on the same DVD.

When I clicked on the Burn button in Nero 7, it straight away progressed to 50% and than gave an error stating that Burn could not be completed.

( Options selected before clicking on Burn were :
Write on the left menu.
Speed was set to 8x, DVD supports upto 16x.
Enable multisession.
Verify data after burn.
)

Now what happened is that the disc has became inaccessible. It is not being read by the Liteon DVD Writer & seems to me like this disc has been damaged.

I tried few of the data recovery tools available on the internet
but were of no use.

Than, I removed the DVD from the tray and turned it upside down to see the recording layer and found that it has overwritten on the previously burned data. This is b'coz there is a big circle round the disc at the end of
and a medium size new circle in that big circle.

Anybody in this forum would have any idea as for how to recover the data from this DVD even though the recovery tools have already been used.

A quick reply in the above matter will be highly appreciable!!!
Apoorva M. Sheth