Are you missing the file path i assume. You need to identify the problem within Device Manager. this can be found through Control panel --> System --> Hardware Tab --> Device Manager. You get a new window, with information relating to all your Devices. If your driver has disapeered, (which by the way is very odd behavior), you will have a "?" in the list. Right click on the neighbouring text, and select "update driver". This will launch a wizard in which you can either connect to the web to search for a driver, or let windows search it's own driver pool on the following page, by selecting no not this time.

In most cases this should update, but thats not to say, that more likely, you haven't got a hardware problem, such as a dislodged cable or something. Let us know how you get on.

The thing is that when I go to the Device Manager the dvd/cd drive device doesn't even appear, it doesn't show a "?" or anything about a dvd/cd driver.

It's quite possible that the physical connectors for your drive have worked loose. If that's the case, the laptop will have to be opened up.

Could it be an ejectable drive. Some laptops come with Ejectable CD / DVD drives, just pull it out, push it back in. What make and model is it?

It's a HP Pavilion Ze5200 which does not have a swappable bay.