File locations in Windows XP
The Photoshop Lightroom application is the Lightroom.exe file, located in the Program Files/Adobe/Adobe Photoshop Lightroom 3 folder.
The preferences file is Lightroom 3 Preferences.agprefs, located in Documents and Settings/[user name]/Application Data/Adobe/Lightroom/Preferences.
The Documents and Settings/[user name]/My Documents/My Pictures/Lightroom folder contains:
Lightroom 3 Catalog.lrcat, the Lightroom database file
Lightroom 3 Catalog.lrcat.lock, which prevents you from overwriting data
The Lightroom 3 Catalog Previews.lrdata folder, which contains additional folders for preview files and data
Catalog backups are saved in Documents and Settings/[user name]/[catalog location]/[catalog name]/Backups/.
Installed and custom presets and templates have filenames ending in .lrtemplate and are located in folders in the Documents and Settings/[user name]/Application Data/Adobe/Lightroom folder.
Registration information is located in the C:\ProgramData\Adobe\Lightroom\Lightroom 3.0 Registration.lrreg file. Lightroom 3 reads the Lightroom 2.0 or 1.0 registration registry entry when it validates upgrade serial numbers. If you upgrade and Lightroom 3 does not find a registry entry for either Lightroom 2.0 or 1.0, it prompts you for a serial number.