False
Whether or not you get any benefit from a dual core processor over a single core processor depends on what operating system and what programs you are running. Newer operating systems (Windows 7, Mac OSX) do use multicore processors. Also, using multiple programs on a computer will better utilize a multicore processor. In short, yes it can make a difference for today's average user.
Any x86 processor from the 386 on up to present-day processors can be used with Windows 98.
Windows XP Professional supports up to two processors
Two. Reference : http://support.microsoft.com/kb/888732 Windows XP Home Edition will only support one processor Note this is physical processors, NOT cores. All versions of Windows XP will support processors with any number of cores.
2
There are several different Motorola processors. No version of Windows supports 680x0 or 88000 processors. Early versions of Windows supported PowerPC processors, but it had few applications available and was discontinued a long time ago.
Yes. Windows Vista fully supports quad-core processors.
XP HomeThe Home edition of Windows XP---the edition that came with most machines home users bought from the likes of Dell and HP, before Windows Vista---supports only one processor. This means if you want to install more than one processor and you run Windows XP Home, you may need to switch to Professional, or upgrade Windows to a newer version with support for multiple processors.XP ProfessionalIf you want to use two processors, Windows XP Professional is the way to go. While this advanced program cannot run more than two processors, this is an improvement over Home. Note that, because dual-core processors count as a single processor, you could theoretically have four cores with this license or even eight, if you are willing to buy two quad-core processors.
Windows XP and Windows Vista, Intel's Hyperthreading did not exist before these Operating Systems. Now I may be wrong here, but I am confident that hyperthreading is a technology built into the processor itself, and any operating system should be able to utilize it. You are right to the extent that Hyper Threading is built into the processor itself, but a chipset and OS which supports hyper threading are also required. Here is the link which gives the list of OS which supports Hyperthreading http://www.intel.com/support/processors/sb/CS-017343.htm Windows XP supports HT Technology ,but widows and windows 9x/me does not
Probably not well. While Vista is an older version of Windows, it is still made for a multicore processor. The best OS to run on that CPU and speed would likely be Windows 2000. Also, machines that are that slow likely don't have much memory.
Enterprise Edition
As an absolute, that may never be known. Officially, Windows XP requires a 233 MHz Pentium processor. Experiments conducted by various people have run Windows XP on processors underclocked to just 7 MHz.