Diagnose a dying optical drive?

[Rockstaru]

I bought a couple of DVDs last night (was in the grocery store and they were on sale), and was ripping them to my computer using DVDFab. The first one (Troy) worked with no problems, but the second two (The Thing and White Noise, was a double pack for $6.99) refuse to rip no matter what I do--they get about 60% into the process, and then slow to a crawl. I tried using AnyDVD and Handbrake to just convert directly from the drive to an M4V, and that put out a file that plays fine for about the first 55 minutes and then is completely scrambled (both video and audio) for the remaining 40 minutes.

Is there any way to tell for sure what the problem is here? I've tried the DVDs in both drives, and both have the same problem. I tried playing on of the DVDs in my desktop and it crashed Windows Media Player at 56:41. White Noise plays fine in another computer. I also just ripped The Thing successfully on my laptop. Is it a problem with the optical drives, or is something else the cause? It seems like something else must be, since the problem occurs in both drives, but is there a way to know for sure?

Thanks.

[levish]

imo, if it happens on both drives i'd rather blame the disc than the drive

[Rockstaru]

So would I, but it worked fine in my laptop, and an incompatibility between the drives and the disc seems unlikely (two different manufacturers and two different drives--one's a DVD/CD-RW, the other a DVD-RW.)

[levish]

if the 1st disc worked but the 2nd didn't (and in general other discs work fine in the drive), I'm going to say that its almost definitely the disc