The drive won't be visible inExplorer or My Computer - but should be visible in Disk Management.
Control Panel - Admin Tools - Computer Management - Disk Management.
Then you can remove previous partitions and make new ones to format for Windows.
You should certainly be able to select (say) half of it only for Windows use - though I don't know how you would set the other half up for a Mac.
I know you could for Linux and BSD so I would imagine you could for Mac - just don't know how.