|I have never burned in Vista, but with Windows 7 there is an extra step involved. After you drag and drop and you think you are burning, you still need to click on the burn button before anything happens. Perhaps that is what happened to your files.|
You should never rely on only a single copy of any files you need to keep. Burning to disk is good but also saving on another medium is safer. As was stated, rewritable optical media is not as good as the write once, DVDR or CDR.
"The thing is, while my PC recognizes the fact there is data inside, when I open it up I only get an 100% empty, writable space." That statement is contradictory.
I don't ever use re-writable DVD media but I think that because you need to prepare the disk before writing to it, the computer will acknowledge that the disk is ready to be written to.