Meging two videos side by side

Hello. I'm average computer user that is trying to do some basic video editing. My knowledge of avisynth and video editing in general is very rudimentary. So this is my issue: I have two uncompressed avi files with same resolutions, same frame rates, same length (in frames) that I would like to "glue" together to one video side by side. It would be something like before-after show-off. So result would be that both videos are playing at the same time, one on left and one on the right. Resolution of new video should keep height but width would be doubled. Is there maybe easy way to do that in with VirtualDub? With AviSync I have found that AddBorders function allows expanding video frame but I don't know how to insert second video. Btw, I found that avisynth documentation is hard to follow if you are not familiar with these "video" terminology. Thanks.

StackHorizotal() Code:

In Avisynth, try: Code:

Thanks guys, I didn't check that one in help files. PS. These freaking random questions by forum are killing me. Name popular mpeg-4 avc encoder? I have no freaking idea! Successor of mpeg-4 avc? WTF. I need to use goggle to post replay.