What do I do if someone else has stole my W2 and filed my taxes?

This is the closest I could find to reporting it.
How Do You Report Suspected Tax Fraud Activity? (http://www.irs.gov/individuals/article/0,,id=106778,00.html)

Hello br:

Get another copy of your W2 and file your taxes as you would normally. Include a letter with your return telling them exactly what you said here, and give them the perp's name and address. Send your return certified, return receipt requested.

excon