One of the problems nowadys is that we all register for websites (Tesco, Amazon etc) using our email address and password.
If you use the SAME password to register for a (dodgy?) web site as you use for your hotmail account, then when you register for this website you are in effect giving away your hotmail email address and password which can then be stolen.
One way round this is to NEVER use the same password as you use to logon to hotmail to register for a website, keep them different.
A friend of mine registered for a "job" webiste to post his CV and used his "normal" hotmail userid and password, the next day his hotmail account was hacked.
User a DIFFERENT password on hotmail than the one you use to register for websites.