Let me add to Johnathan's observations...
While different sweeps rules can differ from State to State a general rule followed by all is to get an affidavit signed if the prize is over a certain value (for tax purposes and as evidence of prize claim). Usually this is $600 but many companies require an affidavit regardless of the prize. Your first notification will usually include a request to recieve, sign and return an "affy" before your prize is awarded.
When the email needs to explain that payment is in USD that should be a red flag to you. I doubt PCH would need to explain that you're getting paid in US Dollars as opposed to Japanese Yen.
When an email asks you for name, addy, phone etc... my first thought is identity theft. They don't need your bank info and SS to cause damage. Besides, didn't you already fill all that info (name, addy, etc) out when you entered the sweeps? Also, why do they need to know your gender and country? It's a USA sweeps (RTFR). And your nationality? C'mon, what sweeps have you ever entered that requires that information? Even the Goya sweeps doesn't ask for that!
Look for typos or obvious cross-culture syntax errors. PCH is a USA company and will go to lengths to make sure there is no question about the validity of your winning notification. And as for PCH notifications, Publishers Clearing House notifies their winners either by mail or by the Prize Patrol showing up at the winner's doorstep. PCH does not notify winners by telephone. Be very careful not to confuse a legitimate PCH win with a scam using the Publishers Clearing House name. Read more about sweepstakes scams here (copy/paste):
http://www.google.com/search?q=how+to+tell+if+a+sweepstakes+is+a+scam&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a
Use common sense, it's your best defense against scammers.
Was the email directed to you personally - i.e. "Dear Gail" or just "Congratulations!"? A legit "winning email" will address you by the info you entered when signing on to that sweeps. The same applies when you get emails from "your bank" telling you to update your info - they will ALWAYS address you by name (or acct info) and will never ask you for routing numbers, SS, and so on. This may not apply to smaller, less value prizes but certainly does to "bigger" ones.
Also, I've never seen a winning email that told me I was the winner - it's almost always says "You're the
potential winner" because if you don't reply then the prize goes to someone else so THEY'RE the winner, not you. You're only a potential winner until the affidavit is signed, sealed and the prize delivered.
You can always contact the real sweeps sponsor and ask your questions about legitimacy. All legit sweeps will have contact info in the rules or on their website. In the case of PCH, if you are ever uncertain whether a win is really from PCH.com or not, you can contact them toll-free at 1-877-3SWEEPS (1-877-379-3377) Monday through Friday, 8:30 a.m. to 5:30 p.m.
Sorry you didn't really win - would have loved to share it with you, LOL
Hope this helps,
Fish