What is the name of the file?
Look in Add/Remove and see if it is there. If so, try to uninstall from there. If it is a program generally they just cannot be deleted they have to be actually uninstalled.

it's not a program. it came up in the music search on limewire and he downloaded it "accidentally". but here's the weird thing, yesterday i downloaded the free trial of Norton 360 and when i went to go scan the file it disappeared before i could. literally, it was there one minute, i right-clicked on it, something else popped up, and then when i went to try it again, it was gone. so now i can't even look at it to be able to tell ya'll anything else about it. i just know that my comp has really been messing up since he downloaded it.

Are you saying P2P file sharing is happening on the computer without an anti-virus program? VERY DANGEROUS. You need to have an anti-virus program AND a firewall on there. You don't need free trials of anything. There are several very good FREE anti-virus programs out there without resorting to free trials.
If you computer has been messing up since he downloaded whatever it was then you need to go through at the steps given HERE Ignoring step 3 but continuing with the rest of the instructions. When you have completed all the scans then post back here with the ESET Scanner Log, the MBA-M log and also a HiJackThis log.
We'll take a look and see what is going on.
Judy