If after you install Windows 7 on your computer and you cannot access the DVD drive, or you can only intermittently access the DVD drive, then this article may interest you.
This issue may occur if you use one of the following DVD drives on the machine:
– Sony BC-5100S DVD
– Sony BC-5600S DVD
– TSST TS-L633B DVD+/-RW
For methods to workaround this issue visit Microsoft KB975270.