Problem: PXE boot option will not map a drive (default F:) to the DS. All the configuration seems correct and the password has been verified.
Altiris uses a LAN Manager Hash file to store and use the password. Most security polices require the hashing of passwords to be disabled for the domain /server. This is normally disabled via group policy in the Network Security: Do not store LAN Manager hash value on next password change setting being enabled.
In most environments it will not be possible to enable this setting across the domain due to security policies. But you can do it for local accounts if you move the server in question to an OU where a policy over the Network Security: Do not store LAN Manager hash value on next password change to disabled. After the policy propagates reboot the server and create a new local account for PXE booting. You will now be able to use this account in your PXE Boot options, just use workgroup as the domain. Once the password is set you could re-enable the Network Security: Do not store LAN Manager hash value on next password change as this setting only applies during password changes.