I just received an SMS saying it's from Nokia, saying "Try out Nokia Music Store by downloading the free track of the week at etc"
In short, you get redirected to Nokia's music store, where they ask you to download the free Ovi Music Player (for PCs, I forget what it is for Macs). Links are provided there.
Once downloaded and installed, if you open up the player, and click on the store tab, it will have a banner at the top of the page, for the "Track of the Week".
You don't get to choose the track that is free this week. I think Nokia pick that / are given permission to distribute it for free.
… I guess if you have iTunes, you run the possibility of getting 2 free tracks per week. One from Nokia, one from iTunes.
One other thing is, I don't know yet, if the music is locked to your PC/mobile device or if it's DRM free.
(I also don't know if iTunes's free track of the week is locked to the device)
iTunes has a "free track of the week" every week. Even if this was any free track it wouldn't be that great, but since you don't even get a choice in the song, definitely nothing special at all about this.