It is quite a while ago but did you have a virus / malware infestation on or about the 7 July 2011. Malware will target management tools like Event Viewer and Task Manager.
You might have been able to fix the problem using System Restore but most likely too much time will have passed for you to have a restore point predating the presumed infestation. What do you have by way of a Windows XP CD? I suspect you will need to do
a Repair Install and for this you need an original CD. If it is a branded computer which includes most laptops it will be a restore to factory settings after backing up your data files.
Gerry Stourport-on-Severn, Worcestershire, England Enquire Plan Execute