Several photographers have asked about running Lightroom 2 as a 64-bit application on Windows XP x64. Lightroom will not install as a 64-bit application on Windows XP by default because it’s not an officially supported platform for our 64-bit version.(Lightroom is officially supported on Vista x64) But when you run the Lightroom installer and choose to "Open the Specified Folder" in the Files are Ready dialog (Be sure to uncheck the option to "Launch the Adobe Photoshop Lightroom 2.0 Installer") you’ll see an Adobe Photoshop Lightroom directory that contains "setup32" and "setup64" executables. I’ll let you pick the one you think most appropriate.
Again, just to be clear, running Lightroom 2 as a 64-bit application on Windows XP x64 is not a supported configuration. The testing required to certify an additional operating system is a significant effort but there was not enough evidence to suggest that we should completely disable the configuration.
Why all the excitement about a 64-bit version of Lightroom? 64-bit capable operating systems and applications can take advantage of more memory than 32-bit systems. If you have a 64-bit environment with more than 4GB of RAM you’re most likely to see improvement in the responsiveness of the Develop module where Lightroom is loading large amounts of information into memory. (A common misconception is that 64-bit systems will see an improvment in import or export performance. Those operations are largely disk-bound so they’re dependent on the speed of your hard drive for performance improvements.)
There has been quite a bit of discussion around the concept of plug-ins for Lightroom. When photographers think of plug-ins it typically brings to mind very unique or specific filters designed to adjust the appearance of an image. Photoshop has a rich history of supporting these image processing plug-ins. The extensibility of Lightroom is different in that we’ve been focused on workflow extensibility that allows developers and photographers to extend the application as a workflow platform that connects to third party services, allows for custom web galleries or custom metadata to adapt to a photographer’s workflow. Photographers would still like to see image processing plug-ins in Lightroom and I agree with them. But for a plug-in to actually behave like a plug-in it can’t break the non-destructive workflow. There has been a little flurry of discussion around the Aperture 2.1 image processing “plug-in” API and the subsequent utilities released behave less like a plug-in and almost exactly like the external editor functionality that has been available since Lightroom 1.0. If a plug-in requires that a derivative TIFF or PSD file be created and block access to prior non-destructive adjustments it’s not really plugged into the application is it?
However, if external editors are what you need, we’ve got them. In Lightroom 2 we’ve added the ability to define as many external editors as you want. And you don’t have to wait for software manufactures to create a custom “plug-in” for Lightroom, just utilize the existing standalone application like the one available for Noise Ninja. The optimal implementation of an external edit interface at this point is the use of a smart object workflow with Photoshop CS3. I’ve used it many times with PTLens and I really appreciate the fact that I can go back and adjust raw settings after I’ve applied the PTLens correction.(Then revisit the PTLens settings) This is an incredibly powerful link between the raw and rendered workflow and half measures with marketing spin labeled as “plug-ins” are not the highest priority for the Lightroom team.