Finalize prob: after i chose finalize, a box popped up and said sharing requires more memory to be available. Quit imovie and relaunch it.. What should i do to finalize my vid?

The first thing to try would be to close imovie and turn off your Mac. When you turn off your Mac and restart, it will clear the memory.

Also, you do not have to Finalize unless you want to. When you Finalize, it shares a copy in every available size and places a copy in the Media Browser. You can do this in the SHARE menu and create just the sizes you need in the formats you need.