Question I have 8 Logical Processors but in Task Manager, It shows that I have 4

That is strange. Did it ever report correctly?

You could try:
  • Click Start and search for msconfig.
  • Select System Configuration.
  • In the Boot tab, click on Advanced Options.
  • You should see an option to set the number of cores. Change this to the correct amount, click OK then reboot.

Shouldn't be necessary, but this is strange.