The same TeX Live installer is used for Windows as for other platforms, so the general documentation applies. On Windows, the installer is invoked with the command install-tl-windows, rather than just install-tl.
When successful, the installer does some special things on Windows:
If you want to share a TeX Live installation among several Windows machines, see the TeX Live Launcher information.
On Windows, TL includes a minimal Perl setup. It is sufficient for running the TL infrastructure programs written in Perl, such as the installer and tlmgr, but it is not sufficient to run every Perl script. Scripts that come as part of TeX packages may require additional modules, and it is not feasible to satisfy all those dependencies—especially since the particular version of Windows can change what's needed.
Therefore, if you need to run other Perl scripts and the included Perl does not have all the modules, you need to install a full Perl distribution.
It is especially important to be careful when processing untrusted documents on Windows, because in general Windows finds programs in the current directory before anything else, regardless of the search path. This opens up a wide variety of possible attacks.
Thus, we recommend checking for suspicious files in the current directory, especially executables (binaries or scripts). Ordinarily they should not be present, and definitely should not normally be created by merely processing a document.
Although the core TeX programs are robust, to the best of our knowledge, third-party programs may not reach the same level. For maximum safety, we recommend using a new subdirectory for processing.
Only one TeX distribution can be active at a time, because all the TeX distributions use the search path to find their programs. This means that to switch from one TeX to another, e.g., between TeX Live and MiKTeX if you have both installed, you must (at least) change the search path.
However, the individual shortcuts – including a command prompt – have a modified searchpath with TeX Live in front, so as long as you use TeX Live via the menu, you should be fine.
Administrator privileges are not automatic even when you run as administrator. So if you want to install for all users, you need to right-click install-tl-windows.bat and select ‘Run as administrator’. The same is needed when running tlmgr (TeX Live Package Manager).
TeX Live is designed for shared use: you can install TeX Live on a network for use on client workstations. All it takes is adding TeX Live to the searchpath.
On Windows, a bit more is expected: double-clicking a file should open it in the right program, there should be menu shortcuts, and the user should not have to worry about modifying the searchpath. A conventional Windows installation takes care of these things.
The TeX Live Launcher can take care of the Windows-specific items in case TeX Live is already present, e.g. on a network share. Configuration takes place when a user runs the launcher for the first time, and Start menu shortcuts are replaced with controls within the launcher itself. The launcher uses an ini file for its configuration.
The launcher is present in the 2016 release of TeX Live. The 2017 release offers the option of making the installation launcher-based, and the included tlaunchmode script can convert a local installation between classic mode and launcher mode.
Full documentation is available on CTAN.
For old TeX Live installations the old client scripts are still available.
The sad truth is that in many cases the cause of the failure is never found, but here are some things you can try:
<path>/install-tl-windows -v -gui text