Uninstalling Cygwin

Here's the rough steps on how to do it, according to the official FAQ.

1. Stop and remove any cygrunsrv services
2. Stop all Cygwin processes and unmount any filesystem's mount with the mount command.
3. Delete the Cygwin root folder and all subfolders.
4. Delete the Cygwin shortcuts on the Desktop and Start Menu.
5. Remove cygwin binary path from your Windows search path, and delete the CYGWIN system variable.
6. Delete Software\Cygwin keys from registry.  

Removing SSHD service

To remove Cygwin sshd in the cleanest possible way:

• cygrunsrv -E sshd
• cygrunsrv -R sshd
• Delete the folder c:\cygwin and all its sub-folders
• Remove the Environment Variable 'CYGWIN'
• Edit the Environment path accordingly
• Start...Run... regedit and delete these two registry trees
• "HKEY_CURRENT_USER_Software_Cygnus Solutions"
• "HKEY_LOCAL_MACHINE_Software_Cygnus Solutions"
• Go to Control Panel, Category View, Performance and Maintenance, Administrative Tools, Computer Management.or click Start...Run...compmgmt.msc delete the sshd user if it exists in the "System Tools" - "Local Users and Groups" - "Users" section.