I have an Astak 250 GB DVR. Its made for recording security video. It has a USB port on it, is there anyway to transfer the video on it onto my mac? Like into iMovie or something, somehow?
Most DVRs made for security systems have a video output. Connect that output to a analog to digital converter (or capable camcorder or VTR) and then capture the footage using the appropriate program on your Mac.
One of the more popular and inexpensive models is the Canopus ADVC110. Or you can use a qualified DV camcorder or VTR that allows analog-to-digital pass through (EE mode).