If you are an AVG user, then it can be possible that you will face compatibility issue with the operating system it is installed on. If you get to see that the Update has detected some running installation, then it is necessary to complete that installation before starting update. And then start the update and see if the new version of antivirus is compatible with the operating system you are using. For best resolution, call at AVG Customer Care Number UK @ 0808-281-8685 (Toll-Free).