You don't need to uninstall the Duemilanove drivers, they just lie dormant unless you plug the Duemilanove in. It would be a bit of a pain if you had to uninstall drivers to swap between using a Duemilanove and a Uno like it would be a pain to have to uninstall your webcam to use the printer. If you've already done this : http://forums.techguy.org/windows-xp/235959-cannot-find-file-specified-during.html
and you pointed the wizard at the drivers folder (not the FTDI folder within it) , Its scrub Windows and start again time, that is sure to fix it (It fixes almost everything).
Just for you, I tried this on my XP test system, it works fine with both boards (& drivers) connected at once, it can upload to either just by changing the board type & com port in the IDE.
Duemilanove (COM7) and Uno (COM8) at the same time.