I found a discussion about converting PGP keys to SSH keys. The following process is described:
- Remove the password from the .asc key.
- Use openpgp2ssh utility (part of Monkeysphere framework) to convert the PGP key to SSH key.
- Re-encrypt both the original PGP key and the converted key.
Monkeysphere is available for many Linux distros, but I have not been able to found any Windows binaries yet.
However, why do you actually need to convert the key? Physically, it will be the same key, but what purpose will that serve? Why not simply generate a new SSH key?