Just to add to what Scott and SB have already said...
I'm a total Linux n00B and about a week ago I installed Ubuntu 7.10 64bit on a Q6600.
It just installed from the disc without me having to do anything apart from selecting region, passwords etc - GPU, LAN, Wireless LAN etc.....everything just worked. The only thing I had to do was go to the Synaptic Package Manager and ask it to install Boinc for me which it did automatically without a hitch.
There are plenty of video packages to download there too, so I doubt you will have any problems.