Where do I remove everything please? Too many problems with damaged mod or can't see skinns only empty place holders with driver names etc. So unstable
i would delete it from programs and features and rfactor2 in documents and then try it again should work fine that way.
Like mentioned above, don't go to the registry. Go to control panel and uninstall it, deleting the rf2 folder (maybe backup the Packages folder) and then go to My Documents (with hidden folders visible) and check appdata, under roaming I believe.
There should be no reason to touch the registry or the activation data to solve that kind of issue. To cleanly reinstall (leaving those things alone): Save your mods somewhere (thats the rfcmp files, etc). Control panel, uninstall rf2. Find the two locations you selected during install, delete rfactor2 from both places (by default, program files and my documents) Now you can install rf2 again clean, and install mods 1 by 1 to see which have issues.
"...or can't see skins only empty place holders with driver names etc." This sounds like you may have joined a server with players using custom skins. You will need to have skin-sharing enabled in your multiplayer.ini in order to see them. The easiest way to enable it is to start the game in Online Race mode, click "Settings" from the bottom menu in the initial screen, then click the button (so it turns green) next to "DOWNLOAD CUSTOM SKINS" just above the Transparent Trainer settings at the lower right of the Display tab. Now find a multiplayer server and join in. After that, patience is required. When you enter an online server, the skin downloads from the other players happen while you are in the paddock, NOT on track. It could take some time before you have everyone's custom liveries. Until then, you may see "place-holders", or blank-canvas skins on opponents cars.