Well you shouldn't downld exe files & should be wary of files that are obviously too small for what you are seeking. You should also keep your anti-virus definitions up to date. See LimeWire continually Popping up every few seconds & also Opening at System Startup for one way of getting rid of them.
Also WORM_VB.AS
& also How to get limewire to quit popping up every few seconds

You can also do an Online scan: http://housecall.trendmicro.com/hous...start_corp.asp