Please help me irradicate system error popup

Any help to this almost computer illiterate would be most appreciated. I used CCleaner after a popup

announcing a "systems error!"....your computer was infected by unknown trojan.....click OK to download the antispyware program to clean you system (recommended)" I immediately ran

my Norton system scan which quaranteened the bug, but did not get rid of the popup described

above, so I downloaded and ran CCleaner with no success. How can I get rid of the popup and

be sure the adware/spyware is also gone? Thanks

This problem is often caused by a trojan or a rogue spyware program.

Please download and run Malwarebytes' Anti-Malware here and report if your problems are gone.

Another that might well help, from the same company, is Rogue remover.

Some names the files your AV detected, and perhaps a screenshot of the popup, might help. Some of these rogue programs are a right pain to remove.