OT moving from MS SQL to PostgreSQL

Hello.
i have an slightly off topic question, but i hope that somebody might know.

at the moment we have a database on a MS SQL 7 server.
This data will be transfered to PostgreSQL 7.4.5 or PostgreSQL 8 (when
it is released). so far so good.

the question now arises, this current database is used in web
application made with ASP on IIS5. The idea is to move the database and
the application to a linux or unix environment. Is there a tool that can
be used convert ASP pages into PHP (or any other language suitable for
linux/unix), or should we prepare to rewrite most of the code?

Is there a tool, some add-in to apache perhaps that can run ASP code on
linux/unix, this would help to have the system running while we recode
the application.

Any thoughts on how such a transfer can be made?

thanks
stig