Extending Partitions

I know this is going to be an easy one but I don’t work with NT4 that much. When you have NT4 can you extend a partition? I have 4 18GB HDDs configured in a hardware RAID5. I have a C drive where NT and programs are installed and then the rest of myspace is Drive E. I want to install a couple more HDDs. Will I be able to extend Drive E onto these HDDs or will they have to be configured as my F: drive?
Thanks in advance.