I used a program called AVI MPEG RM Joiner and when i joined the movie files together they sound became out of sync. I was wondering if there is a better program to join them together?
Try VirtualDub, if the videos have the same fps and other aspects the same (resolution, audio format, video format, etc). You can find a guide for this from our guide section.
When I use VirtualDub To join the avi files I run out of room and I have 4.5gb free. The files are 700mb, 700mb, and 500mb. Is this right for VirtualDUB to take up 4.5gb when joining them? Is there a way to reduce it?
No, it shouldn't take that much. You've most likely forgotten to check Video > Direct Stream Copy and Audio > Direct Stream Copy options on. Our guides work, but normally you need to follow them to the letter