Hi,
in most of the cases the old CHS-geometry isn't used anymore (it can
handle only 8.4 GB btw), so access to the old/new partitions should be
possible to both the old and the new versions.
There is one exception: some bootloaders do have problems with changing
the geometry, because they need e.g. some additional fixed spaces (e.g.
the sectors directly behind the mbr), hardcoded values etc.
Regards,
Michael Fritscher