It seems to me like the permissions issue and not the Windows 7 issue.
Your ssh key is not authorized so you are getting -
Permission denied (publickey).
You need to create the public ssh key and then ask your administrator of your Git repository to add your
ssh public key
For the people those have come here and are just trying to get their repository and who don't care about the protocol name (ssh / https), those might just want to use the https instead of the ssh (if it's just supported).
So for e.g. you can use below command.
git clone https://github.com/%REPOSITORYFOLDER%/%REPOSITORYNAME%.git
Instead of the below command.
git clone firstname.lastname@example.org:%REPOSITORYFOLDER%/%REPOSITORYNAME%.git
If you are still facing the issue around the access even after creating the SSH and adding it in the Bitbucket account or wherever you wanted to, you need to write the following in terminal on the GitBash, OSX or Linux:
# Lists already added identities (‘ssh keys’)
Then, if you still don't see your key listed then you can add it with the following
# Add a new realname
ssh-add ~/.ssh/ realname
This simply worked for me.