Gabby, CCleaner is safe. It works really well and does not provide options to kill the machine. also it can make some more advanced settings that can make you feel uncomfortable... true. But that is also possible by changing various settings manually on the computer.
Crabby, sounds like the usual spam. How did you find out about the messages that have been send "by you"?
Spammers get their addresses from companies or due to various newsletter, price contests and everywhere, where someone enters an address. People need to be more patient about where they leave their marks - when someone provides a textbox to fill in the address, he probably also wants to use it. Everyone needs to consider that. Also if a website asks for postal address - that is mostly used to send a bill. Why else would someone want your postal address?
I personally use multiple email adresses. I have one for the job, one private, one for selling, one for ebay, one for special occations (when I get a message there I know it's a special one) and one for all occasions where I don't want to type in my other addresses. The spam address is directed directed to the spam folder.