The WD software is setup as a virtual CD, so doesn,t disappear if you format or re-partition the drive. There are instructions for removing it on their website though, which is a bit of faff but easy enough to do. Or you can just leave it, since it doesn't actually do any harm sitting there unused.
And if it's one of the WD Mac drives (which i think the Studio is) then it'll already be formatted for OSX.
Final thing, i can't see any benefit to partitioning the drive to put your Snow Leopard install DVD on it - should be fine on the same partition as Time Machine.
David