If you have a lot of recordings and are willing to go to some expense to save time, the MZ-RH1 or MZ-M200--it's the same unit, MZ-M200 is packaged with a Sony mic--will digitally upload the recordings to the infamous SonicStage.
It's the only unit that does this. And it's costly, probably over $300, and hard to find. But depending on how many MDs you want to transfer, it might be worth considering.
The uploads will be encrypted to play only on that particular computer. But you can then, also in SonicStage, take the copy protection off the recordings and convert them to .mp3 or .wav--which I would suggest doing, since the ATRAC (.oma) format is on the way to extinction.
By the way, there are even limitations on the uploading capability of the MZ-RH1. If your MDs were music downloaded from the computer, then they are not going anywhere. But I assume you're talking about live recordings that originated on the MZ-N1 in SP, LP2 or LP4 format, and those should upload.
Sony's atonement for the sins of MD is the PCM-M10. I almost forgive them. Almost.