Im using
Intel Pentium D Processor 805, 2.66Ghz (Duel Core, EM64T) on
Intel D102GGC2 Motherboard, (ATI Radeon X300 based Graphics) 2GB Ram

I recently tried some distros
Fedora 8 and 9 (i686)
Ubuntu 8.04 LTS (x86)
OpenSUSE 11.0 (x86)

aren't running properly
I'm able to use Red Hat Enterprise Linux 5.0, only when I switch to 'SW Single Processor Mode' in BIOS
Any suggestion?