For a long time now, when I check on the task manager, I see that only about 50% of my CPU has been being used for BOINC projects, with the other 50% going to waste. I have checked every setting I can think of, with no inspiration on how to solve this problem and get it back to 100%, at least while I'm not using the computer, and get it higher while I am using it. How can I fix this problem? Is there any more information I can provide to help solve the problem?

Make sure in your computing preferences, If you're using Boinc 6.1.x or later you're got the following set to:

On multiprocessors, use at most 100%
Enforced by version 6.1+

If you're using a Boinc version earlier than 6.1.x make sure the following is set to the same value of cores (or more) than your CPU has:

On multiprocessors, use at most 4 processors

If you're using Web Computing Preferences, make sure you haven't over-riden them with local preferences, try Clearing the local preferences,
(With Boinc 6.10.x and earlier, that is Advanced>Preferences, then Clear, then Yes.)

and last but not least, make sure you have enough tasks to utilise your cores.

Claggy