CD/DVD drive problems

[Dixie]

Background...PC/Windows XP machine all the way through)  About a year and a half ago, my CD/DVD drive stopped working to play DVDs but would still play audio CDs. 

Shortly after, I had a new computer built in old case and a 2nd CD/DVD drive installed.  Both drives worked for a while.  Then, neither would read and play DVD video, but would both still played music CDs.

Did a system reinstall last month and both drives again worked, until this week.  Now, neither will play a DVD, though both drives recognize the DVD and its menu...just won't play past that point.  Have tried more than one DVD in both drives using Windows player and Nero.  Both drives will still play audio CDs.

Bottom line is I'm at this same point three times now and I'm clueless as to what the problem is.  Any idea of what might be going on, or, more to the point, what I might need to take a look at and where to find it?  I'm not very tech savvy, so be gentle, will ya?