|"what should I do in order to solve the problem?"|
If would help to know which CPU & RAM you have...just putting "DualCore" is useless. Make sure your CPU & RAM settings are correct in the BIOS. If you're running AUTO settings, try manually setting the speeds, timings & voltages. And make sure to use the correct CPU:DRAM ratio.
If you have more than one stick of RAM installed, try testing them individually to see if you can determine which stick is bad. When you remove them, clean the contact pins & when you reinstall them, pop them in & out of the slot a couple of times to help clean the slot contacts.
If the RAM still fails after trying the above, it will have to be replaced.
"If my answers frighten you then you should cease asking scary questions" - Jules Winnfield (Samuel L. Jackson) in Pulp Fiction