You can. But before you do that, I HIGHLY recommend you do some things first.
If you haven't done so already, open up those old tax returns in their respective version of the program, and save them as PDF files. When you save them, elect to save EVERYTHING, and not just those pages required for filing, or just "for your records". Save EVERYTHING to a PDF file. That way, if you need to look at something in the future, or if you get audited, you can open that return in the Acrobat Reader program, and print if necessary.
In addition to the above, I also recommend you print EVERYTHING so that you have a physical hard copy. That could very well save your butt in the future if you should get an audit notification the day after the computer with the PDF copy on it, craps out on you. For people like me with 3 rentals and self-employed, my printouts each year are in excess of a hundred pages. But it's a one time deal each year and I do it.
Also saving everything to a removable medium (or 2 ) like a CD or thumb drive is always wise.
One warning about thumb drives. Most folks don't realize this, but they do have a battery in them. Actually, it would be more accurate to describe it as a storage cell. They generally only last about 5 years. You don't realize the cell no longer holds power until you insert the thumb drive into a computer and find there's nothing on it. that power cell is basically a high capacity capacitor, and it "recharges" each time it's inserted into a powered USB slot. So that's how you can get more than 5 years out of one. If using the thumb drive for long term storage with no intent to access it in the future unless absolutely necessary, it's perfectly possible for it to go dead after about a year. But it's also possible for them to last up to 5 years before the power cell goes dead and you lose everything saved on the thumb drive.
bottom line is, do not use thumb drives for long term date storage. You're better off using a CD or DVD for that.
nscoult:
I'd save the CD's for at least the last 3 prior years in case you ever need to amend a return, or if you have a computer/drive failure and have to reinstall the program. As for program updates, state program downloads, etc. TurboTax only supports software for the current and prior 3 years.