DVD drive letter disappears after burning a DVD

Hi!

I am running Vista Home Edition on a DELL laptop. I used Sonic
Solutions DVD drivers earlier but they were causing a well-known
problem so I removed them.

I use Roxio Creator DE 7.0 to burn DVDs. When I burn a DVD, I face two
problems:

1. After the burn process is reported to be completed successfully,
the drive letter, currently F:\, that represents the DVD drive
disappears. This stays so until I reboot.

2. The worst part is that the DVDs I burn with this combination of
Vista on DELL, are not capable of being read on any other computer.
They can only be played back or read on this computer, which I used to
burn them.

Kindly help.