Hi Just set up for first time. Windows Vista Home Premium and Windows mail.   When sending/receiving we often, but not everytime, get a windows security message asking for username and pword. Whatever we enter it fails. We might return later, do send and receive and all will be ok.
Any suggestions?

Have you got secure authentication turned on, perchance? Go to Tools - Accounts, then click your account and go to Properties. On the Servers tab, make sure "Log on using Secure Password Authentication" is not ticked.