HI, 
I'll very pleased to find you let me give the Answer of these question.
what's the truly different between these two files?why you recommend the last
one I mentioned?
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Windows (from Windows 2000 to Windows 10 and above) installer version
WinHTTrack (also included: command line version)	httrack-3.49.2.exe  
[alternate site]	3.49-2
4 MiB (4195032 B)
(01/Apr/2017)
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We recommend:
Windows (from Windows Vista to Windows 10 and above) 64-bit installer version
WinHTTrack (also included: command line version)	httrack_x64-3.49.2.exe  
[alternate site]	3.49-2
4.3 MiB (4513192 B)
(01/Apr/2017)