I don't know if this is going to be possible for you given your version of Data Protector (6.00, which has been out of support for several years). But changes were made in DP 6.11 to implement this. You need to add a line to the 'omnirc' file
OB2OMNIDR_BLKSIZE=256
To make this change, see the attached document 'DP 6.11 Disaster Recovery Guide", starting on pg 136
echo OB2OMNIDR_BLKSIZE=256 > %SystemRoot%\system32\OB2DR\omnirc
However, as I said, this change was implemented in DP 6.11, so you may not be able to use it
If that is the case, you will have to reload and reconfigure Windows on the server, and restore each Object one by one, with C: being first,and /CONFIGURATION being last