If you have a professional subscription, it is still available in the archives.
Microsoft removed 1507 from its official download site years ago. You cannot legally download it from Microsoft directly unless you are an MSDN subscriber.
A 32-bit OS handles memory differently. If a PC has only 1 GB or 2 GB of RAM, a 64-bit OS would be sluggish or non-functional. Windows 10 1507 32-bit runs on as little as 1 GB of RAM (though not optimally). For lightweight, single-purpose machines, this is a viable option.
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