Unable to open paint.net - no available application.

[Anghellica]

I recently downloaded paint.net and MicroSoft .NET Framework 3.5 Service Pack 1, however when I went to open paint.net, I received a message indicating "no available application to open it with" and to "create an association in Set Associations panel". Since I wasn't sure what to change in the Set Associations panel, I wasn't able to get paint.net to open (and I didn't want to start changing everything and "guessing" so I left all settings as they were.) A while back, I downloaded WinRar and it appeared to have "taken over" some of my files so I uninstalled it the same night (Control Panel, Add/Remove Programs). Even though I uninstalled it, I still see the WinRar icons throughout my computer so I thought to reinstall WinRar, just to see if paint.net would open and it did. Now, the problem is that WinRar is only a free trial for 40 days. After 40 days, I must either buy a license to continue using it or I must uninstall it completely from my computer. Since I can't really afford to buy a license for it, I will have to uninstall it when the free trial is up, which means that I won't be able to open paint.net again. I will be back to square 1 again. Does anyone know of a program or application that is 100% free for an unlimited amount of time that will open paint.net? Or does anyone know what I should change or adjust in my Set Associations panel so that I am able to open paint.net WITHOUT using WinRar? Any help or suggestions would be greatly appreciated. Thank you.