Hotmail is a web based mail client so it can't be set as the default mail program.
Your easiest option will be to install Windows Live Mail. This can be downloaded and installed via "Windows Live Essentials" from Microsoft, selecting the components you want, one of which is called "Mail". It can be used to get email from http accounts (like Hotmail) and also pop3 and imap accounts used by many other email service providers. http://www.microsoft.com/download/en/details.aspx?id=21732
When you have installed Windows Live Mail, open the program and with the Home tab selected, select the 'Sign In' icon in the top ribbon bar to access your Hotmail account.