Thanks for the drivers, I was finally able to install CentOS on my server! The problem is now booting into it...
I hadn't actually used the drivers at the link provided and didn't know they were based on athlon.
I see another post has been sent with the process you need to do. Alternatively, if you have the CentOS 3.1 ISO's you can install that and use the driver disk at the link below (which I know works with this OS version)
Following the install you should be able to just do 'yum update' to take the OS to 3.3 (see the 3ware manual on the process for manually compiling the driver for future kernels).
Jim