Sounds like a Nigerian Counterfeit check scam.  They will want you to *immediately* wire money (western union or Money gram) to them under some pretense.  If you deposite the check, it can take up to 3 months for the counterfeit check to bounce and you will then owe the bank for any money that you have drawn from the counterfeit check deposit.

See www.hay-scams.com for more information including images of counterfeit checks and money orders.

I recieved a letter from the "Armstrong Financial Services" stating I had won 250,000 dollars and a real looking check from Wells Fargo Bank $4,580 to use to pay taxes for "non residence" The person I contacted was "Mary Richards". She told me to deposit the check and call her back in the morning.  What a scam, the letter did not have a return address (1st clue) Did not use a metered stamp (2nd clue) and the company the check was drawn on was "Ensign United States Drilling Co.(3rd clue) What drilling company would pay my taxes??? I think I pay big businesses taxes instead of them every April 15th. I did check out the Armstrong financil services as well as the drilling company.  I even called the bank and it is an open account(at least today). I will be turning this over to the attorities in the morning. And I will notify all of the above parties.