I have an RSA key (generated by PuTTYgen) that's set up for logging in to a bunch of machines via SSH. Or rather, i HAD such a key. (The computer it was on crashed, to the point that a reinstall of XP was required. The private key file is encrypted by the file system, and now that it's basically on what looks like a whole other OS and user, whatever XP would do to decrypt the key apparently can't be done anymore.)
What i have left is an OpenSSL-compatible base64 of the public key (from one of the machines still set up to accept passwords), and of course the passphrase to the key. I might(!) still have an old backup of the registry from before the machine died as well, but would have to search for it. Either way, it sounds like it might not be possible to recover the key file itself. (If it is possible, that'd be great. But the prospects aren't looking good so far.)
Is there any way to recover the private key, if i can't recover the actual file that contained it? Perhaps by importing the public key into PuTTYgen or openssl and doing some reverse thing on it? Contacting all the admins involved and sending them new keys could be a pain, so that's pretty much a last resort.