Have you received a tax bill for the previous non-filing years? If this is the case, I would review the IRS assessment to determine if it is correct.
However, if you are making a payment for 2011 taxes owed, you shouldn't be scared to file. You are only obligated to file taxes in years you do not meet certain thresholds of income. It is just always a good idea to file because the IRS may file for you. The IRS filing generally is unfavorable. So filing starts the statute of limitations and allows you to dictate the deductions you take.
In your situation, I would review your non-filing years to determine if you in fact did owe taxes. If not, don't be scared to send in payment. If you did owe taxes, these years can be assessed by the IRS at any time in the future. This would be a much larger issue that may require a tax professional.
Got to a tax service. Do not go directly to the IRS, that is like talking to the cops.
The information provided in this answer does not create an attorney-client relationship. If you are interested in his legal services, feel free to call Chris at (303) 409-7635 at his law office in the Denver Tech Center. All initial consultations are free of charge.
This is a no brainer -- go directly to a tax service!
In no way am I offering you legal advice, and in no way has my comment created an attorney-client relationship. You are not to rely upon my note above in any way, but insted need to sit down with counsel and share all relevant facts before receiving fully-informed legal advice. If you want to be completely sure of your rights, you must sit down with an experienced criminal defense attorney to be fully aware of your rights.
Call a Low Income Taxpayer Clinic in your area. You would likely qualify and they are good at this sort of thing.
If you go directly to the IRS, the risk is high that you will make information mistakes, not know your options, make inadvertent admissions, and be punished more harshly than you would otherwise be by getting professional help. If you do qualify for a low income taxpayer clinic, that is not a bad place to start. However, a local CPA should also be able help you file past returns and get current.
I would be wary of tax services that promise some result ("settle for pennies on the dollar"), and you should do your research on such firms before you plunk down your money.
This answer or response should not be considered legal advice, and does not create an attorney-client relationship. If you have further questions, I would be glad to discuss your situation further. I can be reached at US - (801) 746-6300, or online at -- http://www.lewishansen.com/attorneys/robinson.html