Here are the few tips to fix high CPU usage for windows 7 OS.
Basically, your computer runs default number of programs in the system while starting the system. These programs which are enabled will consume more time before starting up the PC. So, you can improve performance and prevent high CPU usage by removing the number of programs on this list. Few examples of such programs are torrents, Skype etc. So, just turn of this and you open the app if needed. Turn off those programs by going through below process.
Go to windows icon at bottom left and click on run and then type cmd and command prompt will be opened. ( you can also try windows icon + R )
Type into the Run prompt: MSConfig
Click on the Startup tab.
Just go through the list and turn off the fewer priority ones and you can decrease the usage of the CPU usage and boost up the start process in the system.
Uninstall all the junk software, you can go to through the windows and in search option search for uninstall a program and go through the programs and find the unwanted apps, which may be installed by some automated programs while browsing.
Update all the drivers, go to Run and type devmgmt.msc and view all the drivers and check whether they all are updated and if not update them to the latest versions.
Update the windows version to windows 10, because all the apps now will not support earlier version, as Microsoft wants to push the mandatory update to windows 10 for all the systems, so update to windows 10.
Scan for virus using antivirus or windows defender and remove the virus, if any founded.