Hi, I'm working under the OPT visa and I'll do my first tax return.

According to other people, if I'm under the OPT period, I don't need to pay SS and medicare tax.
But what I heard was this case only considered if I live in the U.S within 5 years.
After 5 calender years, even I'm under the OPT visa, can I still be considered as a non-resident?

Let me make sure my situation.
I came to the U.S. May 2001 and graduated from a university July 2006.
(My F-1 visa expired May 2006, but I renewed I-20 and I have a valid OPT visa)
Then I started working September 2006. So, when I started working, it is already passed 5 years even I'm in a OPT period until August 2007.

Then I need to fill out tax return for 2006.
In this case, I'm not sure about my situation.. am I considered as a resident or non-resident.

If you arrived in country on a F-1 visa prior to 2002, you are considered a resident alien in 2006,

You need to file Form 1040, 1040A or 1040EZ.