Something I started in 2006 is still widely used. I created it originally as I was trying to create ArcGIS 9.1 Personal Geodatabases with ArcGIS 9.2. It wasn’t possible then to create older Geodatabases but Esri eventually added in functionality to create older versions. The reason we need these is that you can use older Geodatases in newer versions of ArcGIS but not the other way around. So if you are on ArcGIS 10.2 and your client is on ArcGIS 9.3, you’ll have a problem sharing data. But if you have a 9.3 version Geodatabase, then you can save your data to that version and share away.
I like this archive because each one of these Geodatabases was created with that version of the software. They will work perfectly since they are natively created. So next time you need to have a 8.3 Geodatabase (You totally know that day will come), you’ll have a native Geodatabase to work with. Bookmark and use!
Special thanks to @GIS_katie for providing the updated blank ArcGIS 10.3 File and Personal Geodatabases.