What is the BIOS key for Pegatron IPMSB-H61?

Does anyone know the BIOS key I should press? I tried every key but anything doesn't seem to work.

My motherboard model: IPMSB-H61
Manufacturer: Pegatron

After browsing the web for a while, I found this manual from this post but I'm not sure if this is the right manual since, the Del key didn't work either.

I'd really appreciate it if someone can point out to me the exact BIOS key so I can try it out and see if something's wrong with my system.

Thanks in advance!

According to the manual page 23:

Just when the computer first starts up (before entering your operating system), press and hold the <Del> key to enter the BIOS setup program. (Press <Ctrl+Alt+Delete> to restart if you missed the opportunity.)

You should fast-press the key repeatedly on boot, since the available time-period might be quite short.