If I think the topic goes to another site. There are several options regarding voltages, which I have not wanted to touch due to ignorance, but I know people who have overclocked this micro to 4.0Ghz, and I have also seen tests on the internet with a P5K (with worse cooling than my P5KR) reaching 520 Mhz FSB, and I am still at 440Mhz, so there is margin, what is not known is exactly where I have to touch.

And to tell the truth, in my day to day and with the use I give to the computer, I think I also do not need more. You always get the curiosity to know the limit of this hardware configuration, but, I also do not want to risk damaging any of the components unnecessarily, so unless I see very clearly how to proceed, the OC will stay like this, which I think is already quite achieved considering that I am an amateur in these parts.

Goodbye, and thanks for the help. Agur

Well, no luck...
After several failed attempts to activate Windows, I called the customer service phone, and after being referred a couple of times to other departments, I finally managed to speak to a technician (who was also Spanish and not South American!!) and he told me that no way, that the Windows I have is an OEM that comes pre-installed on a computer and that it comes with a recovery DVD in case you need to reinstall the operating system, but only if it is the same computer. The moment I changed the motherboard, I lost the license, it's that simple... such a shame, for something original that I had...
Using Windows Anytime Upgrade, and with a key that I got through work, I upgraded from Vista Home Basic to Vista Business, and although I can't activate it (since this key is an OEM from an old DELL that we threw away) for the moment I have another 30 days to solve the problem... let's see if I can do something without having to format the computer or pay for a new key... goodbye and thanks for the help, agur

Enhorabuena por la actualización, ahora a disfrutarlo. El pentium D 915 no es gran cosa pero rinde estupendamente para ofimática e incluso algunos juegos en calidad aceptable con esa gráfica. Saludos

Here I leave you some screenshots of CPU-Z and Aida64.

This first one is of the computer as it was from the factory, old case, OEM cooler, and the Asrock motherboard.

ImageShack - Online Photo and Video Hosting

This one is with the new heatsink, the maximum I could achieve with the Asrock motherboard, from here, the computer wouldn't start.

http://img99.imageshack.us/img99/8264/348se.jpg

And this last one is as it is now, with new case, heatsink and motherboard, and the Bus raised to 400Mhz. The temperatures are after 20 passes with the intel burn test, with which it reached a maximum of 65ºC.

http://img822.imageshack.us/img822/3017/400qw.jpg

I look forward to your opinions and advice. Thanks in advance! Regards! AGUR