It is a windows system that the drive is from and removing the drive letter made no difference as tried that previously.
Def not the boot disk either as the drive is a system drive from a fruit machine actually. Just bugging the hell out of me why chdman cant access as a drive and comes back with error of cant open file ......
as chdman can be used for backing up any drive the fact of a letter assignment shouldnt really make a difference for reading purpose anyway, or should it???
Retried again using different pc, unmounted the drive etc. Now windows drive is Disk0 and the hd backing up is disk1 but still same problem.