smash,
I too have MSI K8n Neo computers here with AMD Athlon 64 chips (3000 and
3200). You can find the drivers for the 64-bit environment on the CD which
came with the motherboard. They can also be found at the MSI Site. Go to
their support section, look for the driver section, enter your motherboard
identification.
I have dual boot configurations also to drive these systems. It allows you
to easily switch between the 64-bit mode and down to the 32-bit mode.
Besides drivers be updated by the necessary hardward vendors, the software
vendors must also update their products. There is a limited number of people
who offer any type of anti-virus / internet security software, which can be
installed in a 64-bit environment.
I guess they are waiting for Vista before this requirement will be addressed.