I'm getting these beep codes - (2 short, pause, 4 short, long pause) - repeating.
I couldn't find the meaning of these codes on the internet, the PC model is Omron NSA-CPU01-E.
Does anyone know what they could possibly mean?
Beep codes are BIOS specific. From what I can tell the Omron NSA-CPU01-E uses the Phoenix BIOS. Here is a link to a page explaining all the beep codes. You want the very last table explaining the Phoenix BIOS beep codes: http://www.computerhope.com/beep.htm
You need to contact Omron directly.
Edit: Seeing as you're from Slovakia Here are the contact details