What client are you using from windows?

I use putty and do the following....

take the private key from $HOME/.ssh/identity

use puttygen.exe to create a passwordless identity.ppk file on windows.

use that identity in the Connection/SSH/Auth property in "putty.exe" or as the argument to -i in "plink.exe" to "pscp.exe".

eg

plink.exe -i identity.ppk fred@aixbox uname -a