You can either do the method Flow posted, or render a 1080p WMV out of the video editor. If you just want the video clip then you might as well fraps it since you can easily fake the real speed of the video, but if you want the ingame sound as well then trying to match up 30fps audio with clips recorded at 10fps ramped up to 99% speed is to annoying to bother with.
Editing with 1080p WMV's is not ideal at all, but if you're recording with ENB and anti-aliasing and you want sound too then it's really your only option. Unless you've got a HD capture card like the Blackmagic Intensity Pro then that's the only option you have. Since I like to use a good ENB config when I record IV videos I just use a no watermarks mod with 1080p WMV's.
EDIT: I wouldn't download any of those texture mods, they all look awful and don't fit with the way the rest of IV looks. They tend to be the same roads as IV but with more contrast added to them. Search for DKT70's HD Road Textures if you want some great road textures, but none of them look as good as the originals.
