I use Diamond CD-Rs, they have a silver recording layer. Thats the only thing that works on early CD drives as the laser power levels are a bit weaker, and adjusting the power levels on these older pickups are pretty much signing a death sentence. Bad idea. Also older drives dont read CD-RWs becuase of the beam scattering. its slightly different on the CD-RWs compared to CD-Rs or real CDs. the beam alignment from the scattering shifts enough where the tracking/focus servos are reading the error sensors incorrectly, which are located on the photo pickup sensor inside the optical block. 

Single beam pickups rely on PSD (position sensitive device) style sensors surround the beam. As tracking/focus changes the beam becomes oblong and the PSDs pick that error up and the servos correct. 3 beam pickups use a main beam for decoding and 2 side-beams. each side beam lands halfway onto a sensor on each side. and as tracking shifts, the beam shifts with it. So the optical pickup servo corrects. CD-RWs scatter the beam enough to cause problems with older pickups, So newer pickups position those photo-sensors slightly further away from each other. 

But I digress...

I have one of those little panasonic portable CD SCSI drives which doubles as a portable audio cd player. 

it wont read CD-Rs. Except those.