2manyquestions

Ok, so I'm at my girlfriend's mac trying to figure out why she wasn't able to write on her WD Passport and I decide, I ignore why, that I can fix it by formatting the HD, even though I don't know a thing about macs, nor a lot about PC. So I follow this tutorial from the WD website where it says to "partition" it, and I did so, just that afterwards the HD icon stopped appearing anywhere in her mac; I apparently "partitioned" it as a "Disco de arranque" in spanish, I suppose it would be something like a "starting up disc" or something like that in english. That's when it first disappeared. So then what I tried to do to make it appear, was to create a new image on the disk, since I had that option available, and when I tried to do that it got stuck for about 4 hours filling a bar saying "reading disk", when I finally came back to see what happened, it said that the disk was to full to be able to create an image. So what made sense to me, was to take the HD to my very friendly, less unknown windows xp environment to try and fix it. Only that in this environment after I plug the HD in nothing happens, it is not recognized by the My PC window, nor by the disk manager. Please I need help putting this HD to run propperly again, I would very much prefer if it is possible to do it on my PC rather than on her Mac.
Thanks!