When using Attach Table to attach .xls to Access the table does not attach, the following error may occur:
Unable to open data source. Check to be sure your data source information is accurate and you have read access to the data source.
Unexpected error from the external database driver (1).
The Attach Table option in GeoMedia's Feature Class Defintion command can be used to attach Microsoft Excel format (.xls) data to RW Access warehouses such that the .xls data can be used as a read-only non-graphic table in GeoMedia. The Attach Table option acually leverages the use of Microsoft Access "Linked table" functionality and has the same limitations as the link table option found in Access (.mdb).
Unexpected error from the external database driver (1) error:
Microsoft Excel is not a true database and does not force data to conform to database requirements thus a variety of issues can prevent the Attach Table from attaching or linking the .xls file for viewing in GeoMedia. Ensure that all column headers are "database friendly" (no spaces, avoid reserved words, Begin with apha characters). Column values that are based on calculated functional expressions can also be problematic. The attach table process determines the data type for each column by scanning the first 80 or so values, thus it's best either declare the data type in excel or ensure that the first few records have a representation of the data values.
The Unexpected error from the external database driver (1) can also occur as result of a MicroSoft issue introduced by installation of specific Microsoft updates. Based on information obtained from the Microsoft support forums, the updates that cause the problem for each operating system appear to be as follows.
The operating system listed (to the right of the update number) may not be definitive, so you will want to check for all of the updates listed regardless of the operating system for your particular machine.
See also Microsoft TechNet Thread: https://social.technet.microsoft.com/Forums/en-US/45ebe780-967e-4748-a146-9ec7a15626dc/unexpected-e...
In such cases, you may want to attach the table using a different system that does not have one of the KB's installed.