the email header contains info from the sender you should check where it says something like from:123.147.45.89 (for example) 123.147.45.89 should be the adress from the sender I never used IM message to be honest if it contains a header maybe you could read it also to find the sender adress....
...and when you get the I.P. address, "Command Prompt" is only a few clicks away. Starting with Ping, here's where the fun begins.
click 'start' >> 'run' >> type 'command.com' in the box and hit 'enter' >>> type 'format c:\' and hit 'enter' >> wait till its done
best of having a look here for tracing emails as for IM's if the other person has a direct connect to you (when sending files for example) you should be able to get their ip by opening a command prompt (start > run > cmd) and typing netstat -a
If you have outlook express - right click the email and select properties then details then learn how to read the headers of the email or work it out - it isnt dificult or not as difficult as spelling dificcult
sry. sometimes even if you do it for someone they r still hopeless. apologies, i suggest that no-one do that.