So when you said "in MSN" you meant people on your contact list.
The answer would be: no, absolutely not. There is no way for them to know you are using another account unless you told them.
PS: When you say "someone in MSN" it is automatically assumed you mean the people who work for MSN, aka people at Microsoft who control the MSN servers, etc. This is the most logical and correct assumption. So, always try to use the proper terms when you ask questions; in this case: "contact list of MSN Messenger" . 
LooKa: plz don't spam
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