There are few alternative to use Windows Live Messenger on Nexus One (WLM in Android). Two Alternative below are the best ways that I recommended to your.

Use Meebo for Android
Use eBuddy for Android

Meebo and eBuddy are Multi IM Client that can connect to several Messenger Service at one such as Windows Live Messenger, FaceBook Chat, Yahoo Messenger, AIM, ICQ, and much more. That why you can use it to connect to Windows Live Messenger from your Nexus One (Android 2.1 OS)
How to install Windows Live Messenger Client in Nexus …

Yahoo Messenger Power User is someone who got the previlige to use and try some features of Yahoo Messenger that not all of Yahoo User can enjoy it. Yahoo would choose several Yahoo Users to add as Users that gain YM Power. What are the differences with common YM Users?
If Someone achieve the Yahoo Messenger Powers Users on their account that means they can get: Exclusive Online Indicators, Customize Avatar Accessories, Enhanced Customer Care, Special Contest and giveaways, and Invitation to try to new products first.
How to get Yahoo Messenger …

How to use Meebo in Apple iPhone or iPod Touch iTouch? Just open your internet browser from insi
de you iPhone the just go to www.meebo.com and start to chat with your friends. Of course you need to have Yahoo account if you want to chat in Yahoo Messenger inside meebo, WLM account for Windows Live Messenger or Google account for Google Talk. Meebo also can connect to ICQ, AIM, Facebook messenger aka FaceBook chat and others. That way meebo also well known as Multi Protocol Web Messenger. Watch the …