|Could be tricky to pin down. Possibly worth running System Restore to a date before it happened - type it in Search. Otherwise run these malware checks for starters (in the order given):|
(blue "Download Now" button on right).
Download and "Save" the file somewhere. Go to the saved file then double click it to run the program. Use the "Scan" button, followed by the "Clean" button.
Junkware Removal Tool (JRT)
(blue Download button).
Download and "Save" the file somewhere. Go to the saved file then double click it to run JRT. It might appear to have stopped at times or flash the screen but sit tight until it has finished.
(use the "download" button rather than the "buy" button).
Install and Run the program but before running the Scan go to "Settings > Detection and Protection" and put a checkmark in "Scan for rootkits". Quarantine anything it finds.
Please copy/paste the logs on here.
Always pop back and let us know the outcome - thanks