I've tried this utility disc again, to confirm whether my memory of it was good (and it wasn't entirely)! Upon completion it ejected the tray and displayed "System refresh | Xbox successfully updated. || XTL Version 1.00.4020.1" and here's what I found on the disk afterwards eh...
it had not changed the C partition at all (C:/ and everything in it seemed to be entirely untouched, as before, unaltered, without change, no different, the same);
likewise, which suprised me, it had not changed the X an Y partitions;
it had done a format (or purge) of the E and Z partitions;
it had only re-created these entries in the E partition eh:
TDATA/fffe0000 (and for a slightly different test, the music sub-dir was there too)
UDATA/fffe0000/TitleMeta.xbx (re "TitleName=Online Updater Application")