I don't think you can.  Turbotax Online is built completely different and each return you want to file needs a separate account and a separate fee, unless you qualify to file for free. 

You can try calling customer service, but to be frank, I'm not sure why your owning a 10 year old computer would entitle you to 4 free online tax returns. 

See links below for customer support, and the return policy for the CD.

If your income is less than $34,000, you can file using the TaxFreedom edition, which includes complicated forms not normally included in the "regular" free version of Turbotax. The IRS requires it to be a separate web site. https://turbotax.intuit.com/taxfreedom/ You must create a different account to use TaxFreedom, you can't use your existing Turbotax account.  You will need to start over from scratch.  You may also need to clear your browser cache and cookies before logging in.

The Satisfaction Guaranteed policy and claim form are here.

https://ttlc.intuit.com/replies/3301962

https://ttlc.intuit.com/replies/3300041