More information is needed: for example, are shutdowns random or do they occur with some specific application?
Can you offer any insight as to what "windows" (hopefully you mean Microsoft) found and did to your system while accessing it?
Which Windows version?
How old is the main PC? Make and model.
Try using the Windows Troubleshooters to identify and fix any problems.
"WIN" + "I" > "Update & Security" > Troubleshoot (left side of screen)
You can also use the Event Viewer to discover if Windows captured any error codes or warnings at the time of the shutdowns.
In any case, please provide more information and details.