Log is clean. 

 

Right click on the clock and select Task Manager then Processes then click CPU twice.  This will sort the processes by CPU usage.  If the PC is not doing anything then it should have System Idle very high (>95%)  If not what are the top three users?

 

Check that you have lots of free diskspace.  Open Mycomputer and right click on Local Disk C: and select Properties. 

 

Check the memory:

 

http://www.memtest86.com/

 

Also check that the harddrive is not running PIO:

 

http://support.microsoft.com/?kbid=817472

 

Ron