Since my PC is too slow for most game-capturing software (Core2Duo E7200/Radeon HD5700) while running Zerocron, I finally seem to have found a nice and free open source alternative: Open Broadcaster Software (OBS).
All others I tried either were too CPU-hungry and/or had trouble recording sound.
OBS also didn´t perform so good out of the box, I first had to tweak the settings a bit. Basically I changed the H264-encoding to “ultrafast” with medium quality, resulting in low-cpu and hdd-usage. In case you have the same problem, I thought I´d share my settings with you, relevant stuff is marked yellow. Screenshots are from OBS Version 0.657b.