Lightroom 4

This Adobe TechNote lists the locations for the Lightroom 4    http://helpx.adobe.com/lightroom/kb/preference-file-locations-lightroo m-4.html

Lightroom 2 and 3

This Adobe TechNote lists the locations for the Lightroom 2.x and Adobe TechNote lists the locations for Lightroom 3.x Preference, Presets and Database/Catalog files.  The location information provided in the Technote is summarised below:

Mac

The Photoshop Lightroom application is the Adobe Lightroom 2.app file, located in the Applications folder.

The preference file is the com.adobe.Lightroom2.plist file, located in the[username]/Library/Preferences folder.

The following Photoshop Lightroom database files are located in the[username]/Pictures/Lightroom folder:

• Lightroom 2/3 Catalog.lrcat (the catalog itself)
• Lightroom 2/3 Catalog.lrcat.lock (this file prevents you from overwriting data)
• Lightroom 2/3 Catalog Previews.lrdata (the file that holds the preview data assigned to your photos)

Windows XP

The Photoshop Lightroom application is the Lightroom.exe file, located in the Program Files/Adobe/Adobe Photoshop Lightroom 2 folder.

Preferences are located in the Lightroom 2 Preferences.agprefs file, located in the Documents and Settings/[username]/Application Data/Adobe/Lightroom/Preferences folder.

• The Photoshop Lightroom database file, Lightroom 2/3 Catalog.lrcat, is located in the Documents and Settings/[username]/My Documents/My Pictures/Lightroom folder:
• Previews are located in various folders in the Documents and Settings/[username]/My Documents/My Pictures/Lightroom/Lightroom 2/3 Catalog Previews.lrdata folder. They are organized and coded for the application to read, not for users.

Windows Vista / Windows 7

The Photoshop Lightroom application is the Lightroom.exe file, located in the Program Files/Adobe/Adobe Photoshop Lightroom 2 folder.

Preferences are located in the Lightroom 2/3 Preferences.agprefs file, located in the Users/[username]/AppData/Roaming/Adobe/Lightroom/Preferences folder.

• The Photoshop Lightroom database file, Lightroom 2 Catalog.lrcat, is located in the Users/[username]/Pictures/Lightroom folder.
• Previews are located in various folders in the Users/[username]/Pictures/Lightroom/Lightroom 2/3 Catalog Previews.lrdata folder. They are organized and coded for the application to read, not for users.

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Lightroom 1.x

This Adobe  TechNote lists the locations for the Photoshop Lightroom 1.x  Preference and Database/Catalog files. The location information provided in the Technote is summarised below:

Mac
>The preference file is the com.adobe.Lightroom.plist file, located in the [username]/Library/Preferences folder.

>The following Photoshop Lightroom database files are located in the [username]/Pictures/Lightroom folder:

* Lightroom Database.lrdb(the Lr 1.0 database)or the Lightroom Catalog.lrcat (Lightroom 1.1 and higher)
* Lightroom Database.lrdb.lock (the file that prevents data from being overwritten inadvertently)
* Lightroom Previews.lrdata (the file that holds the preview data assigned to your photos)

Windows:

>Preferences are located in the Lightroom Preferences.agprefs file, located in the Documents and Settings/[username]/Application Data/Adobe/Lightroom/Preferences folder.

>The following Photoshop Lightroom database file is located in the Documents and Settings/[username]/My Documents/My Pictures/Lightroom folder:

* Lightroom Database.lrdb (Lr 1.0 database) or the Lightroom Catalog.lrcat file (Lightroom 1.1 and higher)
* Lightroom Database.lrdb.lock (the file that prevents data from being overwritten inadvertently)
* Lightroom Previews.lrdata (the file that holds the preview data assigned to your photos)

>Registration information is located in the Windows registry, in the HKEY_LOCAL_MACHINE/Software/Adobe/Lightroom/1.0/Registration key folder for Lr 1.x

Make sure you don't delete any of the database/catalog files. The only file you might need to delete or remove is the preference file.

Note: database files were created by Lightroom version 1.0 and use the extension  lrdb. Subsequent versions use catalog files for the same purpose and have the extension  lrcat