Maximum PC

I have a Dell Inspiron with an amd processor(2.30 GHZ), 4 GB ram and running windows 7 home. It has been mostly running fine until a few weeks ago when the processor started to run at 100% all the time.
I can find nothing using a great amount of ram or draw on the cpu.
I have scanned with Malware Bytes, Super anti spyware and Norton 360 which is running all the time and supposedly there are no viruses. I have also cleaned with c cleaner and defragged the hard drive and have used system restore with no change and now I am at a loss at what to do next.
Any ideas would greatly be appreciated.

I take it you've opened Task Manager, selected "Show Processes from All Users" and monitored who's using the CPU? Alternatively going to the Performance Monitor?

Pull up task manager (Ctrl alt del) > open the processes tab > click on "View" (menu) > click on "Select Columns" > click on the "CPU Time" box to enable that view, then at the bottom, select "Show processes from all users" (will need to be logged in as an administrator), finally, click on the "CPU Time" headder to sort processes by most CPU time used. If anything other than "System Idle Process" is using more than a few minutes of time, then check the process out in your favorite search engine or at http://www.liutilities.com especially if it's something you don't recognize.

Thanks for the replies,

Under cpu time the only thing other than idle process using just over 2 min is search protocol host.exe and search filter host.exe, using 1:53 and 1:33 respectively.
Is that enough to cause the problem and how to fix it?
As I type this they have disappeared from the top and the cpu is not running as high

Never mind the last part of the last reply it started to run at 100% a few minutes later.

Well assuming these are always the culprits, Windows' search will index the HDD when idle for so long. Normally this is a good thing as when you are not really using the PC for anything taxing it builds a rapid table of file locations for when you want to search the drive(s).

If this is interfering with your using the PC (like it is taking its sweet time ceasing and giving you back your CPU cycles--my complaint) you can turn off indexing (which I do) and/or remove/turn off search (and instead use a better behaved 3rd party search engine like Copernic, which I do).

As for the host.exe, this is pretty generic for a lot of things. I would guess it is probably also involved in the indexing, but it is possible that it is malware which I really hate to bring up. If the AV is up to date and your Internet habits are good this should not be the problem...or your HDD contents could slowing be being made available to some guy in Russia.