Greetings Deirdre'!
I'm glad that you like CheckCD. To fix your problem try the following steps:
1. Insert a CD-ROM (no PhotoCD, Video-CD …). The CD-ROM drive should be
detected correctly.
2. Try to make a DIR under DOS. Ok?
3. Install the MSCDEX.
4. Press the button on the right side (bottom) to choose a CD-ROM drive.
All drives indicated here should work with the MSCDEX.
I hope that will help.
Best regards,
Monika Lutkemeier
CeQuadrat