I have disposed off all my HP Workstations. I realised that they were the problem and expensive for name sake. The only Hp Xeon in my studio is for Graphics and minor titles and intros. I now use ASUS boards and have no serious problems with CS3/4 ON Vista 64, Q9550, 8gb, HDrives 500gb; 4tb; Intensity Pro. Sad there is no driver for CS4, so I use firewire and so far so good alongside CS3 on Intensity
Change the HP and have your peace of mind. I was in the process of getting a bigger HP, but had a change of mind and use the same amount to get two systems