How can I check that I do NOT have joint return with my spouse?

The best way to do this in TurboTax CD/Download is to do it through Forms mode. If you are not already there, click on the Forms Icon. Then when you get to Forms Mode, click the Forms icon again and search for “info”.  Select Personal Information Dialog from the list and click OK. If you are doing only your return, then only your info will be there. If you are doing both your own and your spouse’s return, then your spouse’s info will be there as well, and the option to “Process spouse’s return…” will be greyed out.

To get back to Easy Step mode, just click on the Easy Step icon.

Thanks. I did as you suggested and only my information is listed while the spouse details are greyed out. (The checkbox to process my spouse's return is unchecked but not greyed out) Is there anything else to ensure we are not filing joint returns?