Igor's incorrect about drag & drop, FWIW. Drag sources can provide the files via IStreams and do not have to write the data to temporary files. The data can be sent to the drop target directly from memory if you want.
Re Winzip, I installed it recently to test something and I was really, really impressed... by the amount of garbage they had managed to cram into the installer of what should have been a simple archive tool. It must have taken me 10 minutes to install the stupid thing, click through all the prompts about other software I didn't want and similar nonsense... Really incredible how bad it is now, even before you get to the program itself (which then tries to get you to install even more junk the first time you run it).