There are legimate tax professionals who can help you settle your tax debt for significantly less than you owe; but as the Guru mentioned above, you must prove that the IRS will not be able to collect your entire tax debt. (which is very difficult and would definitely require the help of a tax professional).
Also, you should file your 2007 return as soon as possible - you will already have to face significant interest and penalties for not filing, which are only compounded when you don't pay.
My website www.taxattorneytaxrelief.com
has information on the different types of tax relief programs offered by the IRS as well as advice and information on hiring a reliable tax professional.