After you install the SBS OS DVD when prompted by the HP software you wait for the reboot into the OS setup portion. You will be able to set up your partitions and such in the SBS OS WinPE.
When you reach that point you can insert the USB Flash drive. You can confirm that it has been picked up by the OS setup by clicking the Drivers link in the partitioning window and choosing to install new drivers. The Explorer window that opens will allow you to confirm its presence.
We always name our USB flash drives ANSWERFILE so that it is easy to find in this process.
Philip
