Eli5 How does a deleted trial software knows that you have installed it before and prompt you to buy it if you have deleted it?
When you delete it, it leaves traces that show it has been installed, most likely in the windows registry. Some software used the hardware configuration of your PC (Mac address, serial numbers, etc) as an ID and checks online to see if an install has been previously registered to that ID.
Typically, something like that will store data in something called the *registry,* which is a database that stores application and low-level operating system settings. This data sticks around after you uninstall the software, and a new installation will check for it.
Now, you might ask, can you delete that information from the registry? Yes, but it’s not advisable, since it’s tremendously easy to mess up your computer *bad* if you start poking around in there without knowing exactly what you’re looking at or looking for.