Click start, and type: Device Manager
Click device manager, and once it opens the window, click on the drop-down menu that says: DVD/CD Roms.
Then, right click on any devices that are there, and click uninstall.
Restart your computer, and the device will be automatically detected my Win7.
I can't guarantee this will work, but if it doesn't, then your Drive probably either a. Broke, or b. the drive became somewhat loose from the Motherboard- which would be noticable if it did.