Do you mean all the autofill options which come up i.e. when you type something into the google search box and it comes up with all the other things you've ever typed into Google?
Similarly for email addresses (like on the govermint's e-petitions site) where it comes up with all the email addresses I've ever had on this PC.
If that's what is meant, then I wouldn't mind knowing howing to clear all or some of them off!
Cheers
Whirls