Scroll all the way to the right on the PSP's home screen to select Network, scroll down to Internet Browser and press 'X'.
When the browser has loaded press 'up' to select the address bar. Then press 'X' to jump to the text entry screen. The address you want for the mobile MSN client is
http://mob.e-messenger.net/mobile When you select Enter, your PSP will connect to the wireless network and begin loading the page. When you return to the browser you can save time in future by adding the page to your bookmarks. Press 'down' on the d-pad to select the navigation bar, then select the heart icon. Select My Bookmarks then [Add to Bookmarks].
Now press 'triangle' to view the page itself. Use the PSP's analogue nub to select the email address and password boxes and enter the information you use to sign in to MSN on your home computer. Select Signin.
Wait a moment for the page to load and your buddy list will appear. Select someone's email address to begin a conversation.
The conversation window works as you'd expect: select write to send a message and reload to check if anyone's said anything to you. When you're finished chatting click Contacts then Exit to log off.
nice guide, thanks 
