my computer recently stopped opening downloaded programs. I open the file and the User Account Control window pops up asking me if I want the program to make changes to my pc. I click yes and then nothing happens. This only recently started happening. I think that maybe I accidentally changed a setting somewhere,

If the problem just began recently, you can restore Windows back to an earlier time, called a restore point. This restores backups of your registry and system settings, but doesn’t touch any of your files. It only takes a couple of minutes, and you can undo the process or try another date if it doesn’t fix the problem on the first try. When you aren’t sure where to go, this is by far the safest, fastest, and easiest option to try first. This works best if you use it immediately after a problem shows up. Waiting more than a week or two means the good backups can be too outdated to use.

Press Image+R to show the Run box, type RSTRUI and click OK. Choose a date when the computer was working correctly, and click Next to restore the system files from that date.
Check to see if the problem is fixed. If not, you can go back to step 1 to either undo the restore process, or try another date.

ystem Restore can undo recent changes to the system, without affecting your personal files.