There shouldn't be any 'private keys' for Win98, that would actually be called piracy.
Kento's question "Can you get into windows?" is pertinent and should have been answered because the key can be retrieved from the registry, but only if Win98 is running.
I can actually get it from DOS with a little program I've had for a number of years.
The registry is too large to fit on anything but a hard drive, Zip disk, or CD.
If Win9x/ME has never been installed there will be no registry to retrieve the key from, so as Kento says, call Microsoft.