"Another version of this product is already installed" upgrading from 9.0 to 9.3.3

So, I created a new patched distribution source for "acrobat professional 9".

The original v9.0 distribtion source was patched to version 9.3.3 via an AIP with following patches

AcroProStdUpd910_T1T2_incr.msp

AcrobatUpd912_all_incr.msp

AcrobatUpd920_all_incr.msp

AcrobatUpd930_all_incr.msp

AcrobatUpd932_all_incr.msp

AcrobatUpd933_all_incr.msp

The patched source works fine for new installs, but when I try to use this installer to upgrade an existing 9.0 I get the "Another version of this product is already installed" error. Is there any way to eliminate this? I created an .mst via the customization wizard that mentions that previous version should be uninstalled.

I want to eliminate having an upgrade procedure for exisitng installs and another procedure for new installs.

Only thing I can do now is uninstall the existing version before installing with the 9.3.3 source or create a separate upgrade distribution that does a chained patch install.

Kind regards,

Bart.