Your question does not contain sufficient information to permit me to answer. Depending of the quantity of piracy and the nature of the works or goods involved, you could face serious criminal felony charges and civil charges for violating copyright law and trademark law insofar as you were trafficking in counterfeit goods or works of art, music, film, etc. If your house was raided, you are probably facing very serious criminal law charges and, therefore, you should retain intellectual property criminal defense counsel ASAP.
This post needs more info. Further, you need to seek counsel if there is any basis for the accusation. Copyright piracy involves steep financial penalties and, depending on the case, could include prison.
Well, if the FBI or another agency (e.g., Homeland Security, SWAT) raided your house last week and you got a letter accusing you of some form of piracy, you are potentially looking at criminal copyright infringement charges (a la Kim Dotcom) and should get yourself immediately to the nearest high-powered criminal lawyer you can afford. If you are being prosecuted out of Chicago, call Elliot M. Samuels -- I think he's still downtown off of Madison.
What charges? Oh, a felony with 1-10 years in a federal pen. More likely a civil case with fines of up to $150,000 per infringing item. So say the raid found 30 instances, you could be potentially facing $4.5 million in damages, plus confiscation of the means of production (sounds like that already occurred), injunction, payment of attorney fees (both sides), court costs, turn over your profits, pay lost profits of the plaintiff, etc. This is serious stuff. You better get an Illinois copyright attorney, or if this was a raid by the US attorney and you were arrested, a criminal defense attorney.
What kind of naive are you to ask us for advice and then merely say "got the letter." From who? Accusing you exactly of what? Demanding what? By when? If you want meaningful advice, don't you think it would help us to have some idea what kind of letter you got?
At any rate, you need to see an attorney and not say more here on this public forum. I am in Illinois and handle these cases. Attorney Natoli is, also. Give one of us a call for a free consultation.
I am not your lawyer and you are not my client. Free advice here is without recourse and any reliance thereupon is at your sole risk. This is done without compensation as a free public service. I am licensed in IL, MO, TX and I am a Reg. Pat. Atty. so advice in any other jurisdiction is strictly general advice and should be confirmed with an attorney licensed in that jurisdiction.