Hi mynoriap,
Thank you for the updated information.
I have included a document with detailed trouble shooting steps to take when your computer beeps an error code. I have also included a document on how to test for hardware failures since you were unable to access the other diagnostic menu.
Computer does Not Start and the LEDs Blink or the Computer Beeps
http://h10025.www1.hp.com/ewfrf/wc/document?cc=us&lc=en&dlc=en&docname=c01732674
Testing for Hardware Failures (Windows 7, Vista)
http://h10025.www1.hp.com/ewfrf/wc/document?cc=us&lc=en&dlc=en&docname=c01443317