Okay I am assuming a HDD not SSD, you should see some usage in games but not 99%, have you played for a little bit to see if it settles down after its loaded everything in? If not have you tried defragmenting it assuming its a HDD, if not its likley that it is just a old hard drive and it could be worth grabbing a cheap upgrade if possible.
Also might be worth testing it out on other games if you have any to try?
Maybe others have some better advice though.