There is no option to save form results to a spreadsheet, but it is possible through a little "trickery" to do so. It is often handy to save form results to a spreadsheet for ease of viewing, and for later manipulation of the data. For example, you can later add formulas to your spreadsheet to see totals. (Note that you won't be able to do this while the form is still "live" - that is, while the form is still being used to add data to the results file.) This technique works best in situations where the form will be in use for a specified period, after which the form will no longer be used.
First, set up your form in FrontPage as you would normally. When you have the form the way you want it, right-click anywhere within the dashed lines of the form and choose "Form Properties." Then, under Send to File Name, notice the results are being sent to something like "your web address/_private/form_results.txt". (The folder and file name may be different.) The first step is to change the file extension from txt to xls. Then, click on the Options button at the bottom of the dialog. Under File Format, change this to "Text database using tab as separator" and click OK.
Now when form results are saved to the text file form_results.xls, it will be in a format that Excel recognizes and can present as a spreadsheet. And since we gave it the default Excel extension (xls), when you double-click the file, it will open in Excel just as though it were a native Excel spreadsheet! Although you can use this method to view results at any time, be sure you do not save the file after viewing it in Excel, unless the file is no loner "live" as discussed above. If it is no longer live, you can add formulas and save the file as a spreadsheet if desired.
One possible pitfall involves the _private folder. By default, this folder is hidden. If you cannot see your private folder, in FrontPage select Tools, Web Settings, Advanced. Check the box that says "Show documents in hidden directories," then click OK. You should now be able to see your private folder. This folder is a good place to store files that you do not wish to be viewed by anonymous visitors to your web site.