If you are using an existing database you should not need to create any of the tables including CMS_avatar. Sounds like what you needed to do was create a Kentico install instance but select not to install the database, then attach your existing database to the install.
The most efficient way is to copy your entire Kentico web directory and database over to the new system and set-up as it was set-up on the old (you need to manually create the website in Internet Information Server). Therefore you will have everything the exact way it was
The other way, but less efficient, is to do a clean install of Kentico with a new, fresh database then restore the old database over the new. You would also need to move any added files to the old site into the new.