That's why you need to be the legally registered user. That is by contacting Adobe and asking for help. If you ever have trouble with the product, whether because your computer crashed and you can't deactivate the old installation, or someone found your license key and installed another copy on their machine, there's only one sure way to resolve the problem. This is a little like getting the key to a car you want to buy.

Having the license key is necessary for this step. Typically you deactivate before you uninstall, so you can move the program to a new computer. Generally you activate a product when you do a new install. Users need to activate and deactivate Adobe products from time to time. Part of what you need is the product key.What's vital is that (a) you download the latest version directly from the Adobe site, and (b) you end up with a product that is registered to you on the Adobe site. It doesn't matter a whole lot whether you buy new or used, or whether you get disks or not.This guide addresses the products sold before Adobe went to the subscription model with Creative Cloud. Here's what you need to know if you want a long, trouble-free experience with your Adobe software. There are many fine sellers on eBay and there are a few who are either unethical or unknowledgeable.