Not sure but as a tip, splitting the files is acutally useful. If it
didn't split the files, the ending movie would be massive. You can put
the files in a editing software and merge them.
I'd like to recommend HD video editor to you, I always use it to edit video and make funny video for uploading to Youtube,
it's easy to use and the quality is awesome, you can crop, cut, join,
edit video with it easily. It also embeds many special effects, you can
even add text to video or add background music, that's pretty cool. It worth a try.
Fraps does not compress the video as it records, so there will be lag because it has to write massive files to your hard disk drive.
Try Bandicam recorder. Bandicam compresses the recording video when
recording, and uses much lower CPU/GPU/RAM usage than Fraps. As a
result, you may have much less lag.
Yes if you get an external hard drive
it will reduce the lag you have when recording video. I had this problem
with audio and that is when I got one. To make sure you are recording
to it, if it tells you select a place to save files before you start
recording make sure you select a location on the hard drive, but if it
just automatically has a default location set you will have to go into
settings and change the default to be on the external one. Make sure to
get one that is plug and play and that will make sure it is set up the
moment you plug it in, no settings or things will have to be set up.