Hi Julia,
When you first load a CD into your drive, the firmware will try to read the index track (at the centre of the disc), to ascertain firstly what type of disc is loaded, and secondly what, if any, files exist on the disc.
The first check is necessary in order to differentiate between CDs and DVDs, and also between formats -R -RW +R +RW RAM etc.
Having ascertained the disc type the second check will then attempt to read the content of the index tracks to build a map of the disc content, it is this map which you will see displayed in Explorer, and also what triggers the 'action' box which you received.
The fact that you got a 'blank disc' window indicates one of two possibilities:
1. The disc is genuinely blank.
2. The disc has not been finalised so the index tracks have not been completed.
The only real way of telling if it is the disc or your CD-ROM that is at fault will be to try the disc in another PC (or CD-ROM) to see if that can read it.
Also you could check the remaining disc capacity to see if it is genuinely empty, or if anything has been written to it.
HTH