You may have two separate problems.
'TrustedInstaller' is actually just an annoying part of Windows, which can be got round by 'taking ownership' of the files on your hard drive. See here:
http://helpdeskgeek.com/windows-7/windows-7-how-to-delete-files-protected-by-trustedinstaller/
Multiple pop-ups are usually the result of malware finding its way onto your computer. Download, install and run the free version of Malwarebytes:
https://www.malwarebytes.org/free/
Points to note:
1. When installing, take care to deselect the option to install free trial of the 'PRO' version ;
2. When running it, use the 'Quick scan' option ;
3. Don't be surprised when that 'quick' scan takes over half an hour to finish ;
4. When it does so, click the button to view the results, ensure that there's a tick alongside everything listed and then click the button to delete what's been found.