How it all started ...
In the early days of Windows 95 and 98 it became obvious that the layout of the Windows OS platform was configured for the purposes of support. Support techs, whether Microsoft or OEM, could use a script of questions to discern a customer's problem, then use scripted solutions for the answers to those questions. Everyone's Windows installation had every component located in the same file paths, so telling a user where to go and what to do to fix a problem was the same for everyone. This reduced the time and associated costs for support, and is an effecient business model.
Hardware at the time was advancing rapidly, but Microsoft was not necessarily reconfiguring Windows to take full advantage of improving hardware. The primary focus of the Windows configuration was still targeted toward efficiency of support. Motherboards were available with two EIDE connectors, each capable of supporting two HDD's for a total of four HDD's, communicating via 80-conductor ribbon cables through UDMA. The hardware could send/receive data from more than one HDD at a time.
To log into Windows required reading data from three folders, \Windows, \Users and \Program Files. Could the process be speeded up by putting those three folders on separate HDD's? Yes, indeed, measurably and noticably faster. Not only was login faster, programs loaded faster, and copying files between HDD's was faster. I have never looked back. A necessary tool in my re-configuring of Windows was drive imaging, so I no longer needed Microsoft's support. My support now came from drive imaging.
My #1 suggestion, my top recommendation for success as a Windows user, is to commit to an established regimen of regular drive imaging.
My daily driver desktop is dual boot. The A side is carved up similarly as described in Partitioning Options, but using Microsoft supported techniques for moving User folders and Program Files/(x86) folders. The B side is carved up using the methods in Tame 10.
The advanced techniques are geared toward separating Windows into manageable portions that become simpler to backup and restore using drive images, easier to customize and repair, resulting in increased stability, improved efficiency, and reduced vulnerability to data loss. This can be accomplished in Windows XP, Windows 7, 8, 8.1 and Windows 10 but the techniques are quite different.
The tools I use are fairly simple, many are already included in Windows, and those that aren't are either free, shareware, or very low cost. They are also quite powerful, and should be used with care. I highly recommend a full system drive image before you start modifying your system.
The same caution applies (a full system image) if you are having malware issues, and are attempting repairs. If somtheing goes awry, it's nice to be able to start over at the last place you had success. Also, if you're working on malware issues, it is a good idea to make a drive image at each stage of significant improvement, so that you don't have to start all over again if something goes south on you in the later stages.