Thought I’d do a quick post on this as there is precious little to be found in forums about this task sequence ‘bug’. I say bug, really it’s probably just lazy programming (I haven’t checked the specifics but the evidence leads me to believe this is the case).
Anyway…the scenario is this:
SCCM R2 SP1
MDT 2013 U1
In this case the Set Variable For Drive Letter step under the Install section had set the OSDPreserveDriveLetter task sequence variable to TRUE which caused my OS disk to be set to X: for some reason! I suspect the same may happen if the OS had been installed on another drive other than C: but I haven’t tested this so can’t say for sure. Equally it appears to happen only with Gather Only Local Data. In any case the fix is to ensure you are installing to C: