1./ i have uninstalled Paint.net, removed remaining folders from HDD, cleaned registry with CCleaner
2./ installed again Paint.net, custom installation(view picture)
3./ at the end of the installation i have unchecked start Paint.net and manually restarted PC, even if app itself does not require restart
4./ behaviour is still the same. on right-click edit will jpeg opened in MS Paint(Windows 7)
Both registry keys seem to be OK
HKLM\SOFTWARE\Classes\jpegfile\shell\edit\command and HKEY_CLASSES_ROOT\jpegfile\shell\edit\command
My user profile HKCU\SOFTWARE\Classes\ does not contain key for jpegfile, maybe that is the problem..