migrating a business application from D4 to D2009

[a.riz...@gmail.com]

Hello everybody,

The company I'm working for has a big Delphi 4 Enterprise application
running on hundreds of desktops with WinXP and Win2K. It's a business
application working with a DB2 database and local Paradox tables
through the BDE.
Now we have to make a general review of this application, adding lots
of new functionalities and changing many things, so we thought it
could be a good idea to upgrade it to a newer version of Delphi
(Delphi 2009? 2007?)

Do you have any idea of the effort that will be needed for the
migration? What (if any) thing could need to be rewritten? Which
issues could come? And which version do you suggest to upgrade to?

I know it's quite a general question but any suggestion is welcome.

Thanks.