Cannot play commercial CDs???

[NotMe]

OS: WinXP SP3
DVD/CD drive: Maxtor

Last time I used the drive to play commercial CDs, about a month ago, it worked fine. Now, although it will play CDs I burned myself (same computer, same drive), it refuses to play commercial discs!

I've tried 7 of my commercial discs; none will play with either WMP or VLC. Nor can Explorer/TotalCommander "see" those discs.

Any suggestions, please?

 

[NotMe]

Postscript:
Cleaned all 7 commercial CDs; cleaned laser head.
Re-checked WMP and VLC; both confirmed as up-to-date.
Still cannot play commercial CDs, but can play self-burned CDs.
Might this have anything to do with DRM?