VirtualDub (http://www.virtualdub.org) and NanDub (http://sourceforge.net/projects/ndub)can do that. I recommend NanDub if you have VBR (variable bit rate) audio since it’s better at avoiding out-of-sync audio/video.
Open NanDub (VirtualDub has the same interface, so the steps are identical). Open your video file (or drag it onto the NanDub window). Click Video, Direct Stream Copy (very important, otherwise you’ll get an uncompressed AVI which is humongous). Now at the bottom, you can see the timeline. Now you’re at the start. Click Edit, set selection start. That marks the starting point. Then move the time thingie to about a third of the way through the movie. Under the timeline, you can see a bunch of arrows. There’s a couple of them with a key on them. That navigates between keyframes. You *can* make your cuts at points other than keyframes, but that tends not to be very accurate. So click the key button left or right a couple of times - that *should* not take you too far from the 1/3 waypoint. Now go to edit, and choose set selection end. Go to file, save as AVI and pick the name for the first third. Then basically repeat the steps for the middle and last thirds. Select starting points and ending points, and save the portions. Let us know if you get lost!
Try to use VideoCharge.
This program allows to split video on time, on the size, on a part.
Also splitting of files can be executed without decoding and coding of each file that will save to you a lot of time!