Choosing which version of windows you need can be a very difficult job. I shall try and make the choice simpler for you.
Windows 95.
You should only get Windows 95 if your system is more than 4 years old, and you have older hardware which might not be recognized by the newer versions of windows. Windows 95 might be a little speedier because of its lack of intergration with Internet Explorer and lesser system requirements, but it probably isnt your best choice, unless you run a company or something and you can save lots of extra money on buying an older Operating system.
Windows 98.
Windows 98 is a good choice for those of you with not exactly new systems, but not old systems either. Computers that are 2 years old or so should be good with this operating system. Windows 98 is a little slower than 95, but it has more perks, such as the nice web intergration, Universal Plug and Play, and Active Desktop. Another nice feature that Windows 98 has is the shading of the title bars, that doesnt really matter as much as productivity goes, but its a nice look. Windows 98 also comes with an updated version of Internet Explorer 4, and a few new System tools.
Windows ME
Windows ME is not for older systems. Its very slow on older systems, but once again the new enhancements are really worth it. Especially System Restore, which saves you tons of time by letting you undo changes you made to your system, just like going back in time, but you wont lose any of your new documents and things like that. It also installs software very easy, with a new updated install wizard. Windows ME also has an automatic update program, that searches for updates to your software and hardware so you dont have to. It also comes with a windows scandisk program so that you dont have to run scandisk in dos anymore when you shut down incorrectly. One major downfall of ME is its lack of support for DOS. If you have ANY dos programs at all, I’d think twice before buying ME.
Windows 2000 should be used only by those people who have use networking stuff.
My recommendations
Pentium I or Cyrix with 32 MB Ram - Windows 95
Pentium II or AMD K6 Or Celeron with 32 - 64 MB Ram - Windows 98
Pentium III or IV or Athlon with 64+ MB ram - Windows ME