Public ReadOnly Property InstalledSources As Variant

This read-only property returns a list of all the installed TWAIN devices, in the form of a collection of strings. Note that traditional TWAIN devices will appear in the list if their driver is installed on the system, whether or not the physical device is connected or turned on. On WinME, WinXP, and later platforms, WIA devices will appear in the list prefixed with "WIA-", but only if they are connected and active.

Here is a fragment of VB that gets the list of installed sources, and loads the list into a Drop List combobox called DevList. The last line makes the default TWAIN device appear as the selected item in the combobox.