Some Windows 10 users can face RunDLL Sysmenu.dll error. The issue, in the form of pop-up message, occurs when Windows is starting. Let’s try to figure out what is the RunDLL Sysmenu.dll error. Well, it is not the system error. Actually, Sysmenu.dll error is just a part of malicious adware, which means, from now on, a lot of intrusive ads will be displayed on every webpage you visited. Mainly, the information produced by such ad is related to discount coupons.