why such the users exist?

[kwfine]

I am using WinMX 3.31.
Normally, when the files are searched, the users' names will be displayed.
But recently or I've never noticed it before, some of the users' names are displayed as "Unknown", and some even with their names as "C:\my_documents_and_settings".
 
can these users do harm to my PC?

[Me Here]

Not likely to be able to damage you no..

I am curious where you are seeing this
Is it in a browse, search...etc...