I replaced an LG CD-ROM for a Sony one, everything is plugged in, is set to master, and recognised in BIOS. Ejects and reads discs... but Windows XP won't recognize any discs.
Possibly, yet unlikely. I'm assuming you used the drivers from the disk? If so, try reinstalling. Also, try booting your XP cd with the drive, if that works that at least rules out it being a complete DOA (although the writing capabilities may still be non-functioning).