As far as i remember, it uses 'GetStoreLocation' which you set in global settings - but changing this will change that link in all the places it's used eg when you click the logo link, message templates, 'home' on your navigation breadcrumb ... and many others
If nobody else has a better idea for you then I suggest you make the change in the above mentioned files - whatever way you do it will invlove a change in the basic structure - I think here is best