I was in OPT till September 31st of 2008. From October 1 2008 I am in H1B. Which tax form should I file? Is it 1040EZ(Non resident) or 1040 (resident alien)?

Thanks
Ashwin

If you are single, then file nonresident tax return if you did not complete 5 years on F1/OPT.
Read about F1/H1-B tax filing: Your U.S. Tax Return: The U.S. Visas