I really don't have any idea why it would do that. If it's the exact same DVD you took to your friends computer and it worked fine then its obviously not the DVD unless you have scratched it or something since then. And Nero says you have DVD-read capabilities, but not Dual layer. Are you sure the DVD isn't dual layer?

Do other DVD's work in the drive?

And you say you have tried just typing "H://" in the run line?

Does My computer pop up fine when the DVD isn't in there?

Maybe try opening Windows explorer by right clicking Start and going to Explore.

I don't know. Weird.