Ok this is how it is. OCZ runs @ 2.8V and Patriot runs @ 2.6V. I tried doing what is above and unfortunatelly, first boot i got a long beep, second beep i didn't get a beep at all.
And I was so happy at having 2GB of RAM. ;/
EDIT: OK. I moved the voltage to 2.8V and put in both RAMs and the computer booted perfectly and everything. So everything seems to work, however, when i go to Control Pannel --> System it only displays 1GB of RAM. When I open up Everest it tells me there are 4 sticks of 512 RAM. Windows doesn't seem to detect it, What Can I do?