Hello axel,
Before addressing the beep code, please unhook any devices you have plugged into the computer, such as printer, scanner, camera. Then try starting it.
According to hp that beep code is associated with a cd/dvd burner issue. Open up the computer, and pull the power cord out of it. While you have the case open, clean out any dust that is inside, overheating may be causing the issue. Place cover back on, and try starting it.
Next step is to reseat the hardware inside your computer, this involves removing components such as memory, video card(if present), and any additional hardware you may have.
Next remove extra hardware, If it is non-essential try starting your computer without it being installed.
including a link to common beep codes to use as a reference, They will change depending on the hardware you remove, such as memory, video, and the processor.
http://h10025.www1.hp.com/ewfrf/wc/document?lc=en&dlc=en&cc=us&docname=bph07107#N196