Hang onto your money. This is a well known scam. It's been going on for years and years and years, and the only thing that ever changes about it is the name and location of the company that supposedly has sponsored the contest and the amount you (never really) won. This is not how a real contest works.
If this contest were legitimate you would never
have to prepay a thing in order to get your winnings. Having to pay an up front fee -- even if it's only $20 to start -- is the single biggest tell-tale sign of an advance fee contest fraud. Any legitimate contest would subtract any and all transfer fees from the amount that they were going to give you and send you the rest free and clear. The only reason for the unnecessary step is that they have no money for you. In fact the only money in your dealings with them will be yours, and it will be headed in only one direction --- from you to them and never the other way around. Further, if there's a company really behind this you would never have to pay off a private individual.
In a real contest there is no such thing as a winner chosen randomly from all the email addresses in the world. You must enter a contest in order to be able to win it. They are just phishing for your money and for any personal information you are willing to give them that they can use to commit identity theft
Cease all communications with these scammers and if you have given out sensitive personal identifying information, take all precautions against identity theft. Once you give them money, as you can see, they will simply come up with more reasons for you to send more money. But if you stop sending it they are not beyond hacking into your account if you have given them the means to do it. Cut your losses now.
Here are some other things you should know about lottery and sweepstakes scams:
-- If you never bought a lottery or sweepstakes ticket or entered a contest in the first place, there's no way you can win it. Don't let anyone try to convince you otherwise.
-- No legitimate lottery makes you pay them anything up front in order for you to collect your winnings. If there are any real transfer costs, a legitimate business will deduct them from your winnings and send you the rest free and clear. No charge. No partial payment send some back. What you won you get without having to send in a dime.
-- Any unsolicited offer asking you to send money by wire outside of the country is a fraud. A wire transfer is the scammer's safest means of stealing your money because it is instant, irreversible and untraceable
Call your local police to report the fraud and the FBI, online at IC3.gov as the only chance you have of recovering your money is if these thieves can be apprehended.
You can read more about these kinds of scams here on Snopes. And everything you might ever want to know about contest scams, you can find on this very helpful anti fraud site. (See link)