Mike got an error message that something had stopped working when he installed DropBox. He uninstalled it, but the error is still popping up. Leo says it sounds like the uninstall didn't get rid of all the necessary files and so the Windows registry keeps referring to them. He should go to DropBox and see if they have a removal tool. He can check his services in Task Manager too. That will tell him what it is and he can at least disable it.
Leo also recommends using Microsoft's SysInternals. There's some apps in there, including AutoRuns and Process Explorer, and they should help him narrow the issue down. He can then use Piriform's CCleaner to clean up the registry. Mike should do a backup first. He can also just try reinstalling DropBox and see if that fixes it.