Hi I have a mesh which I have already defined vertex groups for the bones but have not parented to the armature yet. I want to parent the object to the armature without losing my vertex groups (whenever I press armature deform envelope weights or automatic weights, my vertex groups are cleared and blender inserts its automatically calculated vertex groups for the bones). Is there a way to do this?
You can select your mesh, go to the properties panel, assign an armature modifier and choose your armature as "object".
If you use Ctrl+P , "Armature deform" is the same, as long as you are sure not to have choosen "with empty groups", nor "with envelope weights", nor "with automatic weights".