Possible software with support for converting of bak files to xls file format.
It is only possible to convert .bak files as excel spreadsheets (.xls) if these backups actually contain some kind of table, spreadsheet or database in first place.
Typically, programs simply rename the extension from original to bak, so no conversion is needed, just rename the file back (in this case .xls) If this doesn't work, then you probably have no way how to reliably convert the data, because bak is too much of a generic file extension and you would need a special file identifier to determine what file type it actually is.
Updated: October 14, 2016
Unfortunately, there is no detailed software record in the database for this conversion.
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