User Login Names

I hope this is right forum.

When I go out to several web sites where I'm registered, when I click their

logon (login) textbox and type the first character, a list of user names to

select from appears. The list is just my current or former usernames, Not

every user name that might exist on the server loging onto that begin with

the first character typed.

I noticed recently, that my actual name appeared in this list because my

logon username happens to start with my first name. I've NEVER used my

actual name on any of these sites -- period!!

I've searched the registry and I cannot find my user names anywhere on my

system. Where does this list reside on my system (file name and directory)

OR is this some type of virus or malware?

How do I stop or edit the list?

Thanks

David