I had the same problem with the built-in Intel graphics card and the older
variants of Knoppix. Strange graphics and then rebooting. I tried some other
Linux distros some time ago, I cannot remember which and the results were
automatic reboots. Windows NT also causes automatic reboot. The major Linux
distros (Ubuntu, Suse, Fedora, Mandriva and their derivatives), the new versions
of CentOS, Mepis, Knoppix, Sabayon are not a problem for this PC. 2000, XP,
Vista and 7 are not a problem either. 98 installs fine but then, "your VGA card
is not supported" or something like this, 95 installs fine but then it says
there is not enough memory.
So your problem could be compatibility with some components.