>We have a large amount of code which captures a data set and then gives it to a user as a spreadsheet. We've been using COPY TO (filename) XLS and, for the most part,
>this has worked well for us. We haven't run into too many issues with large data sets (these were broken down into multiple sheets and have a different routine if the dataset contains memo fields.
>
>I'm now running into situations where we are going to have a significant number of datasets with more records than COPY TO XLS can handle and I'm looking for advice on the easiest way to turn them into XLSX files.
>
>I have some ideas (do the first chunk as XLS. Convert it to XLSX. Do the extra chunks as XLS and then COPY/PASTE the records) but they feel clumsy and I'm sure there has to be a better way.
>
>All feedback appreciated.
>
>........... Rich

I had a similar situation and solved it by first copying to a CSV file, then using Excel Automation to import the CSV file and saving as XLSX.