All I've tried has been for i386. I don't know if Celeron can handle 64-bit OS (I might can it later, cat /proc/cpuinfo |grep lm). I have also tried many other Linux distributions and OSs: Debian 5.0 is fine, Ubuntu 9.04 is installed and fine, in 9.10 mouse and keyboard won't work but boots, OpenSuse 11.3 didn't boot, but got pretty far. Chakra (I think it had Linux version 2.6.34) got stuck after it had booted, but anyway I won't install it on that computer.
Nexenta boots (that's sort of OpenSolaris but with Ubuntu 8.04 programs/packages/something like that). What is the future of OpenSolaris anyway? Now when Oracle has bought it, I mean. I'm not sure should I use OpenSolaris on that computer, because it's not mine but for my dad's work, so it really should work. He has been quite happy with Ubuntu 9.04 until now. Something I haven't tried are BSD-version of Debian (how stable is it? Compared to Debian testing with Linux) or any other BSD and the real OpenSolaris.
I know this is weird issue, but it won't make it any easier to handle. I doubt Fujitsu will give any support if I ask but I might even try that.