Phillip Corcoran said:
Both XP & Vista have an email client built-in (Outlook Express & Windows Mail respectively) so you probably set up your Hotmail account in those built-in email clients in the past. Under those circumstances, the "Scan to email" feature works because the email software is/was installed on the computer.
Windows 7 does not have any email software built-in, you have to install one (for example, Microsoft Office Outlook or Mozilla Thunderbird).
If you currently can only access your email account by signing in on a web page, "Scan to email" will not work.