Help!!! Please

I had many 'sub folders' containing very important attachments in my 'Windows Mail' whilst using Vista which I can't find now access since updating my system to Windows 7.  

Windows Live Mail has been set up on my new system which brings in any emails that come through via my BT email account but those all important old sub folders I had on Windows Mail (Vista) are not there! Logging in to my BT web email account does not show the sub folders as they were all sitting in Windows mail.  Is there any way I can retrieve these?  BT can't help.

Any guidance would be much appreciated.