When you say 900gigs of memory that refers to drive capacity.. While that should be adequate the message likely refers to the amount of RAM in the machine.
I think the absolute minimum required for FCP is 2GiGs for working with HD and I think 4 GIGs if you are trying to work with uncompressed HD. (although not sure how that machine would handle those kind of files)
So checking out how much RAM you have would be my suggestion in the first instance.