I lost my w2 form for 2007 and already filed taxed but I need it again and it's not available.

Ask your company for a copy.

For various options you can try to get your missing W2, read
Your U.S. Tax Return: Missing Forms W-2, 1099-Misc, 1099-Int, 1099-R (http://taxipay.blogspot.com/2008/05/missing-forms-w-2-1099-misc-1099-int.html)