Disconnect your folders!! Why?
When you open ArcCatalog, a set of entries are inserted into the Catalog tree and a complete scan of your connected folders occurs to identify files of the type you’ve instructed ArcCatalog to show. Of course, many of us may not be aware that we instructed ArcCatalog to do such a thing because we just accepted the default installation.
If you open the Options form from the Tools menu and look at the General tab you’ll see two list boxes. The first contains the top level entries you want the Catalog to contain. The second contains the types of data you want the Catalog to show. By default, all items in these two lists are selected. However, there’s a good chance that you may never need some of them. Thus, it makes sense to tell ArcCatalog to ignore entries and items that are of no interest to you by unchecking them in these lists.
In addition, there’s no sense in having ArcCatalog search for items in folders that you know will never contain GIS datasets. So, it’s a very good idea to remove the connection to the root folder of your drive from the Catalog tree along with any other connections to folders that may lead to unnecessary scanning. Then add as many connections as required to folders containing GIS data. As you should see, adopting this process can lead to a huge improvement in the speed at which ArcCatalog open
This method can also be applied to the ArcGIS desktop software also, you may notice that when you open a fresh ArcGIS session that there is the option to open the session from a large list of your connected folders.