Hi there,
Whilst I've got no direct experience with Windows 7 as yet, I'll try answer as best I can.
Sounds like you may have an older version of Outlook which the Vista/Windows7 code doesn't support. The easiest thing would be to upgrade to Office 2003 or 2007, which are supported to run under Windows 7. That way, you'll be able to setup your accounts as per the setup email accounts wizard and/or menu options.
Windows Live Mail is the replacement for what was Outlook Express, so essentially, you should be able to link up to protocols used by email providers that it supports. Virgin Media I have no knowleddge of either, but you'll need to check 'how' that was setup in your older Outlook (IMAP? or POP3?) and then see if the new Windows Live Mail offers the same setup option. It may be that virgin media have changed the way email is delivered to newer operating systems/versions of office outlook etc, although I doubt it.
A quick search reveals this website - have a quick look
http://www.howto-outlook.com/faq/win7upgrade.htmI'd also put in a call to Virgin media tech support and ask them to walk you through setting up your email account to connect with Outlook.
Hope this helps a bit - Cheers! DtM! West London & Slough UK!