Hi abdin,
You mention running memtest on your computer - how long did you run it for? Normally you need 7 - 8 passes to make sure your RAM's working correctly, so if you didn't, run memtest overnight.
To test your CPU - try downloading and installing Prime95 (Old School CPU Stress Test, there are more newer ones if you google 'CPU Stress Test') to make sure your CPU's alright.
I understand that you can't boot into Windows normally, so, instead, try booting in Safe Mode:
When your computer boots up, repeatedly press F8 (Do this before the Windows Logo shows up)
If you did it correctly, your screen should now show a list of possible boot options.
Select Safe Mode, and proceed to login and view your desktop.
This should...