Quote fromthe frame rates in that world VS what I get in normal worlds is massively slow. windows xp sp3 and that was a old save from around halloween time. it was giving me 1fps all the time. 32 bit and my specs are dual core amd with a decent video card 3g ram. usual frame rate while fraps encoding is stable @ 29fps.
I deleted the nether (yes it was that bad) and regenerated it. Your portal is not in the same place but it is no longer corrupted. Maybe it was because you were using hax? (infinite armor/health = hack)
Here is a link to the world