do you have it installed to your computer?
or is it just the one that opens up when you log into myspace?
if its installed in your computer try this:
'c:\documents and settings\YOURUSERNAME\application data\myspace\im\'
You could also search your computer for '*.txn' . MySpace LOG files are named using the scheme of usersName.txn . So if your looking for, say USER you would look for USER.txn
but if you are using the one that opens when you log into myspace, i wasn't even aware that you could.
i hope i helped out some=]