Installed Snow Leopard on my 1st gen Mac Pro and had nothing but trouble: random crashes and re-boots that have gotten so bad that now it crashes during boot up. Part way through the spinny wheel you get after the boot-up Apple logo either half the screen goes orange (!) and it crashes, or the centre of the screen corrupts and it crashes or I get the multi-lingual grey screen of death. Same happens if I boot from the Snow Leopard DVD. Pretty unhappy as you can imagine: can anyone suggest anything? I've tried re-seating the graphics card , blowing out the dust and I've rotated all the memory: makes no difference.