I usually use GParted from
HERE for such things.
You can also boot from your Windows 8 install disk into a command prompt, like
THIS and then use diskpart commands to clean the disk and partition/format/etc.
HERE is a guide to diskpart syntax, but all you need to do is type in the command prompt box:
diskpart
list disk
select disk n (your target disk)
clean (this will completely erase all partitions and unformat, so you may want a less vigorous command)
create partition primary
format (and there are a number of options that can be used in the syntax)