It's not normal for a computer to be using 99% CPU with background tasks only. I'd format and reisntall windows. If that doesn't work, there's a chance there's a rootkit infection. In that case, the laptop is a no-go for anything.
In any case, as others have pointed out, I don't see a lot of benefit of hanging with this laptop if you already have other computers. Unless you want to retire those devices and use the laptop only?
It's fine to have high CPU usage when something is actually running. I meant that it's not normal to have background tasks (open programs that aren't actively being used) consistently consuming too much CPU. 0~5% would be healthy. Maybe even 10%. Most definitely not 75%+.