Hi, today I am going to show you how to put MSN on your psp.
Step 1: Download
First download Pro Messenger from this website
Step 2: Extraction
Then extract the folder Pro-Messenger with either 7zip or Winrar. After that atach your PSP to your PC using a USB cable. Drag Pro-Messenger to PSP/COMMON.
Step 3: MSN
Now disconnect your PSP and got to your internet browser (on the PSP, not the PC) In te URL bar type in file:/psp/common/pro-messenger/index.htm. Now you have MSN Live Messenger. Enjoy!
I'm sorry if it doesn't work and if it doesn't you could use Ebuddy like Arzon said
P:S I missed out the l in html on purpose, it is just htm.