Windows will normally show the CPU at 100% when no load is being placed (like when you open additional programs) because it uses the CPU capacity to perform Windows op system maintenance processes however it releases the appropriate amount of CPU capacity to other aps as needed when they are opened and used.
Your system malfunctioning (slowing down with certain aps freezing) may be a separate issue.
I would suggest you read the tutorial about using Hijack This, how to download it and create your log, and how to post your log in our HJT forum and then do so.
Please read the pinned post in our “HijackThis” forum,
here Carefully read and follow all directions explicitly.Following instructions, run a HJT log and post it in our HJT forum,
at this link.
Do not as yet attempt to fix anything by yourself using Hijack This. A member of our HJT Team will analyze your log, make recommendations and offer assistance.
It may take a short period of time to get a response to the log you posted because the members of our HJT Team are kept very busy.
Please be patient as this team is manned by volunteers. They will help you
as soon as possible.NOTEOnce you have posted your HJT log,
please DO NOT make any additional posts in the HJT thread in which you posted your log until you get a response from a member of our HJT expert team.The first criteria they have when looking for logs that need replies are posts showing
0 replies. If you make an additional post, it will show as having
1 reply.
A team member, looking to see if a reply has been made might well assume another HJT Team member is already assisting you and might not open the thread to respond.
So, make your post and wait for a response from a team member.