Gmail users should now be used to viewing their messages by conversation. To make it simple, if you have 2 or more conversations of the same subject, Gmail groups them into a single view and when you click on them, it takes you to other messages.
Here is an example in Gmail,
You can I have 2 conversations and 6 conversations in the next. So, when new mail regarding that conversation arrives, it goes into that and I will know something new related to that subject has arrived.
You can do the same with Windows Live Mail :)
Enable the View by conversation by going to the View menu as below
Once you select that, if there are any messages in your Inbox, it gets updated accordingly ;)
You will see a arrow kinda thing at the start if it has multiple conversations,
And if you expand by clicking on that arrow kinda thing,
I like this feature very much and happy that Windows Live Mail has brought in :D
Please implement this feature into Windows Live Hotmail, please :D