sidebarsynch.dll is a SidebarSynch.dll
belonging to Yahoo! Sidebar Synchronizer
from Yahoo! Inc.
Non-system processes like sidebarsynch.dll originate from software you installed on your system. Since most applications store data in your system's registry, it is likely that your registry has suffered fragmentation and accumulated invalid entries which can affect your PC's performance. It is recommended that you check your registry to identify slowdown issues.