Hi Tinchu,
You make a very important point.
Saying “SSE uses only one core†is misleading—and irresponsible if it leads someone to configure his system to use only one core.
While QuestViewer itself may use only one core, the oprating system can use the other cores for disk access, to run other processes in the background, and even to run SSE routines that are called by—and are external to—QuestViewer.
Running a multi-core processor to use only one core forces SSE to share that core with all of the many other processes that are running—such as indexing and, as you mentioned, virus scans.
Regards,
Marty