Obviously you will not be able to format the hard disk whilst still booted into Windows (or any OS for that matter). Best way is to boot the device with a bootable CD/DVD/USB (WinPE/www.ubcd4win.com) and then do a format/re-partition of the hard disk.
except the system drive you can format all other drives
to do that either use right click menu(right click on a drive)
use computer management(right click on my computer), also you can merge drives from there and can create many other drives
but if you want to format complete hdd then you need a bootable disc
or you can use raid utility of bios (if it is there) to do a low level format