I tried Morgan, Mainconcept and PicVideo MJPEG codecs on Win2k ( comes VERY close to WinXP since both are based on NT4 ) and PicVideo was the best. Their Wavelet codec is impressing but too slow for capturing ( unless you have something like Athlon XP 3000+
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PicVideo was the fastest and nearly had the smallest file size ( I compared all codecs with same quality settings and the quality really was the same in all files ). Only 0,5% difference for 1min 15secs to the smallest file ( can't remember which one it was ).