ok, so delete 3.66?

Uninstall it. From control panel - add/remove programs.

Your items and textures and stuff are on the Toribash database or something somewhere, it's not on your computer. So even if you buy a new computer and get a new ISP and move to africa, you will still have all the items you've bought.

Maybe its a glitch, i had to manually put my account into 3.69 from taking it out of 3.66.