Please I need help. I didn't my taxes in 2009 I received a letter from IRS. My case is I live in mexico and worked here only 73 days in 2009 with TN visa as subcontractor, I know is late now but I need to do it. I do't want problems.

It seems you got 1099-misc from your employer. You must file tax return if income is $400 or more. This income is subject to SE tax at 15.3%. So make sure to file your tax return.
You will report your income and business related expenses on schedule C or C-EZ (Form 1040). Then you put net income (or loss) on line 12 of Form 1040. This income is subject to SE tax at 15.3% (this is shown on line 57 of Form 1040). For this you will use schedule SE (Form 1040). Even though schedule C treats you as a self employed, which may not be correct for you, this is how you report this income. Your U.S. Tax Return: Tax Filing by Self Employed Sole Proprietor or Independent Contractor