Our tool reengineers BTrieve databases and converts comprehensively a MS Access Base de datos into a SQL Server Base de datos, unlike the Microsoft’s UpSize Wizard preserving all table structure details, and supports the conversion of the views and procedures. Moreover, the tool supports solution of structural problems between Access and SQL Server like making the implicit behavior of boolean fields in MS Access explicit in SQL Server by setting the default to FALSE and making the field required. We understand that not everything can be converted automatically. First of all, there is the complexity of translating Base de datos functions into their SQL Server counterparts. Add the problem of user-defined functions (in VBA), where VBA code would have to be translated into SQL Server syntax elements in a user-defined function. But there are also decisions to make regarding changes in the client application. Take a view for example with two fields of two different tables with the same name, which is possible in Access but not in SQL Server. MS Access would expose field names like [<table name>.<field name>] in order to make the name unique, but since SQL Server does not allow such a syntax, the fields would need to get another name; with all consequences for client applications using this view. To deal with all these problems, our tool converts everything it can automatically. All remaining items are identified, the problem is shown clearly to the user, and an interactive mechanism is provided. If, for example, a record could not be inserted due to a constraint violation (a wrongfully inserted Fecha like 1/1/199), this insert instruction is logged in a separate error log, and can be edited and executed. When a referential constraint fails, our tool creates automatically a view in both the source and target Base de datos, containing the foreign key records, which don’t match a primary key. Our tool is also prepared to convert from or to other Base de datos systems. Starting with Versión 2.1, any source databases can be converted to SQL Server.