Windows Live Mail is the newer program, and replaces Windows Mail which
comes with Vista.
Both are email programs and newsreaders.
WLM has an integrated calendar which synchs with your online Live/Hotmail
calendar.
WLM can access Hotmail/Live/MSN http email accounts, which WM cannot.
WLM can synch your contacts with the online Windows Live Hotmail, if you
sign in with a Live ID.
WLM can access RSS feeds.
WLM can auto-complete typed in email addresses from the Contacts, WM only
remembers 29 typed-in addresses.
WLM has separate Inbox, Drafts, Sent items, Junk email and Deleted items
folders for each email account. WM dumps all email into one Inbox.
WLM has 37 spell check languages, WM has 4.
WM can let you view the source code when composing a message, WLM cannot.
WM has not been updated since Vista was released.
WLM and WM can now both access Hotmail POP3 accounts, since MSFT has added
that service.
No one seems to like the pale colors, lack of highlighting, and lack of
toolbar icons in the current version of WLM.
Hopefully, MSFT makes some changes in the next release.