if you want zoom feature,no free one available ,sorry to say that.

the best free one with zoom feature is camtasia,but a lit complex if you don't mind

there is only one freeware that works ok which is camstudio.

(but the problem is that it is not good for games)

for games i think you can try the following

1.fraps,works ok for game

2.hypercam,but unregistered version cannot record sound

3.Total Screen Recorder,whcih is good for tutorials and games

http://www.softwarewikipedia.com/index.p%E2%80%A6

i using Total Screen Recorder, it doesnt have zoom,either, but you can set recording area by selecting options such as fixed size, fixed region,

or define region before recording.

http://www.totalscreenrecorder.com/

See if it can help