A. Windows 2000 uses a driver signing system and when a driver is signed its been tested and is known to work with Windows 2000. You should always use signed drivers where possible.
If a driver is not signed and you try and use as part of an unattended installation your installation will stop and you will prompted to continue to use it, this obviously defeats the purpose of unattended so its possible to configure the installation to ignore driver signing.
Open your unattended/sif file and goto the \[Unattended\] section and add the line:
DriverSigningPolicy = ignore
There are actually 3 values for DriverSigningPolicy, ignore, warn and block. They speak for themselves I think :-)
Please note that if you are using drivers that supercede those supplied with Windows 2000 and they are NOT signed the installation process will ignore them and instead used the built in signed versions.