If you're having problems with rubbish messages coming through your Microsoft MSN Messenger or Live Messenger, then follow these steps:

1. Make sure you have an up-to-date virus scanner installed. (This is probably the most important step here!)
   Click HERE for a guide on Virus Scanners
   
2. Make sure you have the latest version of your messenger application installed:
   • For Microsoft MSN Messenger or Live Messenger download from HERE
     
     
3. Change your Messenger password
   1. Sign in to your account summary page with your Windows Live ID. (The e-mail address and password that you use to sign in to Windows Live programs and services such as Windows Live Hotmail and Windows Live Messenger; Microsoft services such as Xbox, MSN, and Office Live; and anywhere else that you see the Windows Live ID logo.)
   2. Under Password reset information, click Change next to Password.
   3. Verify that the e-mail address in the Windows Live ID field is correct, and then type your old password in the Old password box.
   4. Enter and confirm a new password - Make this password secure - user numbers and letters!
   5. To set your password to expire every 72 days, click the Make my password expire every 72 days check box, and then click Save.
      
4. Ensure you only receive messages from your friends:
   1. In the main Messenger window, go to Tools > Options (click the down-arrow in the top right on the window)
   2. Go to the Privacy tab, and make sure “Only people on my Allow List can see my status and send me messages” is ticked.
   3. Click OK.
      
5. Keep an eye on who's adding you as a friend:
   1. In the main Messenger window, go to Tools > Options (click the down-arrow in the top right on the window)
   2. Go to the Privacy tab and make sure “Alert me when other users add me to their contact lists” is ticked.
   3. Click OK.
   4. Now, when someone tries to add you to their contact list, a dialogue box will ask if you want to allow him or her to contact you. If this request is from a stranger or someone you don’t want to hear from, tick “Block this person from seeing when you are online and contacting you”, then click OK

If you're still having problems, it may be worth trying a more thorough virus scan (one that checks for other types of nasties too), for this, try Trend Micro's free "House Call" online virus scanner at http://housecall65.trendmicro.com/, follow the default options, and accept, and be prepared for it to take a while - possibly a few hours.

If you're still havng problems after all that, there's a more than likely chance that it's your friends with the virus - send them the link to this page and get them to follow these steps.