My question is how backwards-compatible is Client Access Express with previous versions of Client Access?
What did you mean when you asked if Client Access Express was backwards-compatible with Client Access? You would not be able to have more than one release of Client Access on a PC at a time. On the iSeries you can have more than one release of Client Access.
As far as your other releases of Client Access, you should be able to connect to the iSeries the same as before. There will not be an issue with having two different Client Access releases connecting to the AS/400.
This was first published in June 2001