Hi retrobit64
I am Dave, I will help you with this.
SysMain is related to the Search Indexing process in Windows, it was previously known as SuperFetch, it is known to be very resource hungry and the best option is to disable SysMain, it is not required.
Click your Start Button, then just type Services and press Enter.
Scroll down the list of services to find SysMain, then double click that service.
Stop that service and set its Startup type to disabled.
Save that setting and restart (not shut down) your PC.