It shouldn’t be too complicated.
Have you tried with default password on a optiPoint 4x0 web management interfaces (clearly a subnet scan, as suggested above, should let you find all the IP devices for the considered subnet)?
Have you tried 123456 as the Administrator password on a IP terminal’s WBM page or directly on the Phone’s display (you have a complete management menu then)?
Have you read about optiPoint 4x0 on the wiki.unify.com (http://wiki.unify.com/wiki/optiPoint_410/420)?
Then you will be able to find the HiPath 2030 LAN IP Address to which all the optiPoint 4x0 are registered.
In the best case the HiPath 2030 could still have the default Login ID/Password (31994/31994).
I have installed and managed few SIEMENS HiPath 2020/2030 (V1 and V2) years ago and, trust me, you don’t need any USB Driver once you find/set the communication system’s LAN IP Address: as written, a normal Web Browser should suffice once you’ve found its LAN IP Address.