VIdeo card configuration problems.
At first, I thought I had problems with grub:
#204: Configure grub for dual boot
but it seems that grub is properly configured after all.
The problem is that the grub menu doesn't display when I boot the computer.
It seems to be a problem with the video card. When using linux on that computer, I saw some strange artifacts within console and man pages (some words were truncated).
I need to find out what video card is inside (it's an Acer computer, ready assembled) and figure out what driver problem there may be.