You need to covert the E and F drives to dynamic drives. These are separate physical drives, right? not partitions?
Assuming they are, and once you convert to dynamic, you can either create a simple spanned volume or a RAID-0 volume. A spanned volume just fills up the first drive then the second, but shows as one drive letter. RAID-0 will alternate between the two drives, so it will be faster.
Beware that you have to delete any exisiting volumes and format the new volume, so move your data!!!