sometimes I receive some strange emails stating that I can receive a
big amount of money if I can contact the mail sender and give them my
contact info, identity provement and other things. I don't believe
free lunch, but I have interests to know how they cheat. following you
may find a sample email. Thank you.

Rememer, all winning must be claimed not later than 30th May, 2006. 
Please note, in order to avoid unnecessary delays and complications, 
remember to quote your reference number and batch number in all 
correspondence.Furthermore, should there be any change of address do inform our 
agent as soon as possible.

Once again congratulations.
Best regard,
Maria Suzzy,
Lottery coordinator.

The information transmitted is intended only for the person or entity 
to whom or which it is addressed. Unauthorised use, disclosure or 
copying is strictly prohibited. The sender accepts no liability for the 
improper transmission of this communication nor for any delay in its receipt
- ESPAŅOL NATIONAL LOTTERY

Any time there is an email that claims you have won a lottery, you
know it's a fraud. Real lotteries do not notify winners in this
fashion. But thieves do: either they will ask for some sort of
processing fee before disbursing your "winnings," or they are
"phishing" for information that will be used in an identity theft
scam.

You have received a variation of a 419 fraud

419 is the Nigerian penal code for 'Advanced Fee Fraud'
- sadly the majority of these frauds are perpetrated by Nigerians

Basically they want to get you to send them money, before you collect
your 'winnings' - but they are quite versatile and would use any bank
and personal details you send.

Here is a link that explains it:
http://www.ic3.gov/crimeschemes.aspx#item-12

Here are some more links that give you an idea of the things they get up to:
http://news.bbc.co.uk/1/hi/uk/1438872.stm     Joseph Raca
http://www.419legal.org/
www.scamvictimsunited.com 
www.fraudaid.com 

Google on: 419 nigerian advanced fee fraud
http://tinyurl.com/43rx6

http://www.419eater.com/forum/
http://home.rica.net/alphae/419coal/
http://www.carbuyingtips.com/fraud.htm

In a recent issue of "The New Yorker" magazine is a terribly
interesting article on how such scams work, from the point of view of
the victim. The story is available online:
http://www.newyorker.com/fact/content/articles/060515fa_fact

Since they rely equally upon the victim's gullibility and greed, they
are classic "confidence games." See Wikipedia:
http://en.wikipedia.org/wiki/Confidence_trick

How is greed a motivation here? How can one win a lottery one has not entered?

Thank you my friends who have paid attention to the question and spent
time to give me comments. I think I got answer already.

You have certainly got an Answer

In return, you could consider making all your friends and
acquaintances aware of what you have learnt.
- it will protect them
- and help 'dry the well' for the scammers

You were sensible asking here