Just had to clean out another laptop, this one Windows 7. I ran the usual cleaning procedures. how-to-get-rid-of-most-malware
After all was said and done, the Chrome browser seemed to be misbehaving. Task manager showed a constant CPU usage of almost 50%. I installed Process Explorer to see what was going on. https://technet.microsoft.com/en-us/sysinternals/processexplorer
It turned out to be a process called Lsass.exe. This process was running from the C:\Windows\System32 folder as it should be. Running from anywhere else could be a sign of an infection. Anyway it only seemed to spike with Chrome running.
I found a quick fix on line. Uninstall and re-install Chrome. In Control Panel go to Programs and Features, Find Google Chrome in the list of programs, right click and click on Uninstall. It will ask you if you want to delete browsing data. Saying yes will delete your bookmarks, by the way. Your choice.
Once done, use Internet Explorer or another browser to download aand install Chrome again. In the case of this laptop it seems to have done the job.