sounds like WD it hiding something on the drive they dont want you getting rid of lol. either that or the system put a pagefile on the drive lol. one way to find out would be to put it into a linux box and format it from there to whatever file system you want to use. if you still get the same result, what software are you using to check for hidden partitions? the latest version of hiren's boot CD has a ton of great tools for figuring out things like that, and if all else fails you can always just zero the drive using DBAN