Use a tool called HandBrake, to compress the file from several Gig to only a couple MegaBytes with no loss of quality or resolution.
I LOVE this, encoded a 3 GB video to 78 MB, barely any quality lost, no freezes, no sound delay, no noticable FPS drops etc. etc. I wonder why Fraps doesn't have this built-in :3
Yeah I love it very much as well, I found it a while back while searching the interwebs, it's really awesome and powerful. But most importantly it's FREE