Core i5 3570 using only 2 cores out of 4

[kreemo]

i upgraded from a Intel Pentium dual core to intel Core i5 3570 3.40hz that has 4 cores 4 threads but my pc using only 2 cores i tried every possible way to enable all cores although my BIOS shows that i have 4 cores

is there any way to fix this problem ?​

[AlHill]

Do you know for sure that your motherboard bios supports the i5-3570?  Most do not unless you update the bios (with the old processor).

Did you run the chipset inf software (provided by your motherboard/system manufacturer)?

Doc (not an Intel employee or contractor)
[If you find any Intel driver you might need, download and save it now.]