I think I have been able to answer some of my own questions.
Also, how can I tell which svchost.exe is associated with which application. In task manager I only ever see one svchost battling away at 99 - 100% during this time
but I don't know what its doing. I don't see any other usage of memory or
cpu by anything else.
I installed Process Explorer which is able to provide a lot more information.
the svchost that is hogging resources is PID 1128 (is the PID the same on all machines?? )
New PID's are assigned each time the PC is turned on although the number will stay in the same range because of the order in which they are loaded.
At this time, there are 4 other svchosts, PID 908, 980, 1160 & 1248. They are accessing a lot less dll's. 55, 44, 37 & 54 respectively so the culprit is running as much as these 4 put together..
The number of dll's running under a svchost is immaterial. The same number of dll's will load each time.
A point to note, is that I do have IIS installed (??) and that may be causing a problem.
I inactivated IIS and everything is running smoothly.
So, to summarize, IIS was causing the
CPU to run at 100% for at least 5 minutes.
IIS was using 12 DLL's. The number of DLL's in the svchost dropped from 175 to 163 after inactivating IIS. I'm not sure what those DLL's were. I wish I had taken note. Maybe one of them is corrupt??
My options now are:-
reinstall IIS and if the problem returns note the dll's being used and replace them one by one.
Install apache
Not run either.
That's something I will have to ponder. I am closing this thread as the problem is resolved.
Thanks to all who replied.