Flash does not install adaware/malware browser popup ad hijacks. You could not have downloaded Flash from Adobe's site? Never install Flash or any browser or media plugins from a third party site. It's not unusual for these to contain malware.
Download and run
AdwCleaner and
Junkware Removal Tool. These are FREE portable apps and don't need to be installed. They will remove most current hijacks, adaware, and other browser based malware.
System Restore does not remove browser hijacks in many cases as it does not fully snapshot browser specific configuration changes.