You probably need to get a new CD-ROM. I've seen many situations where older (ie. low speed like 6x) CD-ROMs just can't read burned CDs. In terms of reflectivity and appropriate wavelengths for reading them, burned CDs are a bit different from "real" CDs and as such only newer burners can read them. An additional thing to consider is the speed at which the CDs were burned. I've heard (though I've never seen a technical explanation why) that a burned CD cannot be read in a drive rated slower than the burn speed. In other words the slowest drive that will read a CD burned at 8x is an 8x CD-ROM drive. These days it won't cost you too much to get a plain CD-ROM drive that'll run at 24x, 32x, 40x, 52x, or whatever suits your needs.