"My parents came to the states two years ago, they have been working since 2004 but they did not make taxes last year. I am going to send both years of income tax (2004 and 2005) but should I send them toghether in the same envelope? They need an itin so a w7 form is also neccesary, with which year should it go? Thank you for your time. J.D."
You should mail the returns in separate envelopes. Mailing returns in the same envelope is often considered "bad luck." Busy data entry processors at the IRS service centers will sometimes think everything in the same envelope belongs to the same year. So, please mail the returns separately. If you want to mail everything in one envelope, you can. But put each return in a separate envelope, and then put each envelope into one big envelope.
Also, enclose a copy of the W-7 with each return being filed. In the box where you would normally place the Social Security Number or Individual Tax Identification Number, write in the words "ITIN TO BE REQUESTED."