A Worm for Windows disguises itself as iTunes – Macitynet.it
It is an archive named "iTunes.exe" the Worm that is circulating in these days also through AOL messaging AIM: a message is sent "This pictures never gets old" linked to a specific URL from which to download the worm, but the archive could also be found in the availability of P2P services.
No problem for Mac users (as known sheltered from worms, viruses and dialers) but some risk (which Trend Micro categorizes as "low") for users with Windows operating system.
If users download the "iTunes.exe" archive of dubious origin they can find on their computer a 'WORM_OPANKI.Y' file that opens a random TCP port and connects to the IRC server xyz.legi0n.net and through the IRC channel #fate can receive commands from an external user and execute them on the local machine. It can also download and run Adware-type applications on the affected machines.
For more information, refer to this page on the Trend Micro website.
The suggestion to give Windows users, however, to download iTunes.exe directly from the Apple site and to be wary of archives made available in unsafe places.