The following is a tutorial on posting to your blog on MSN Spaces using the W.Bloggar desktop blogging application.
Create a Space on http://spaces.msn.com if you don't have one
Go to 'Edit Your Space->Settings->Email Publishing'
Turn on Email Publishing (screenshot below)
Choose a secret word (screenshot below)
Download and install the latest version of W.Bloggar from http://www.wbloggar.com
Go to File->Add Account
On the next screen, answer "Yes, I want to add it as a new account" when asked whether you already have a blog
Select 'Custom' as your blog tool and choose an alias for this account (screenshot below)
Select your Custom Blog Tool Settings as shown (screenshot below)
Specify your provider information as follows; Host=storage.msn.com, Page=/storageservice/MetaWeblog.rpc, Port=443, HTTPS=checked (screenshot below)
Enter your username and password. Your username is the name of your space (e.g. I use 'carnage4life' because the URL of my space is http://spaces.msn.com/members/carnage4life). The password is the secret word you selected when you turned on Email-Publishing on your space. (screenshot below)
Click Finish.
Go ahead and create, edit or delete blog posts on your blog using W.Bloggar