DVD drive only working sporadically

I have a Toshiba Equium A200 and am using Windows Vista. A few months ago my DVD drive started playing up. Most of the time it will not read or write data, then suddenly it will read a disc that it previously couldn't read. Then it stops reading it just as suddenly. I've spent hours reading forums and haven't found a fix. Any ideas?

Thank you

I don't know how to check the data and power connections (not very computer savvy) but assume they are OK because my DVD drive plays music CDs and commercial DVDs without problem. It also occasionally and randomly reads data files that previously and subsequently show as being blank. The drive shows up in Computer, but when I put a disc in it comes up with "702MB free of 702MB" as if the disc is blank.

I've checked the registry key that crops up again and again in forums, and there are no values for upper and lower filters listed.

I have uninstalled the drive and rebooted. It is listed in device manager without an exclamation mark, and says the device is working properly.

I looked online for how to update the firmware and got a warning that this should be done as a last resort only. I'm worried that I do it wrong and mess things up even more!

Any more ideas would be gratefully received?