Missing CPU thread

Do you have any Core unlocker features if so i would look into those

Remove the check mark from number of processors. That is what is shutting down one core. If you select 2 then it will shut down 2 cores and so on. Remove the check mark and reboot.

According to this that CPU is a Dual core with 4 Threads check if Hyperthreading is turned on

it could be issues with a bad bios settings Intel Core i3 2310M Notebook Processor - NotebookCheck.net Tech

PHarahap136 said:

what is RMA?

http://en.wikipedia.org/wiki/Return_merchandise_authorization

Advance options is used for testing. Number of processors is confusing. It should read (Number of cores) It is used to shut down the number of cores you select. If the check mark is removed all cores will work if nothing else is broken or set wrong.

It should read (Number of cores)

Isn't it actually cores and threads - like in hyperthreading. The i3 has only 2 actual cores.

Well I have never had a chip with just two cores so I don't know what it will show.
Check your 4 core system and if your system is using all four cores I believe you will find in advanced option their will no no check mark.
Just like in my posted picture.
What I have found that the advanced options is use to shut down cores when checked not activate them.