The .HLP files are Windows help files which were once used extensively by all the Windows programs. Then starting with Windows Vista, Microsoft decided to drop the support for .HLP help files in favor of modern and newer CHM (Compiled HTML Help) files. If you happen to have an older program that you cannot stop using and it comes with legacy .HLP help files, then you cannot view them. If you double-click on an .HLP file in Windows 8, then it shows the help window explaining why you cannot view the program.
If you have an older software or program that uses the legacy .HLP files, or you just want to open an .HLP file, then you can add support for them by installing a downloadable update from Microsoft. In the knowledge base article KB917607 Microsoft has detailed how the support for .HLP files has been dropped and how you can install a Windows 8 version of WinHlp32.exe.
The WinHlp32.exe program can be downloaded from Microsoft Download Center. The download does not require a genuine Windows validation but you can download using the following direct download links shown below :
For Windows 8 32-bit : Windows8-RT-KB917607-x86.msu
For Windows 8 64-bit : Windows8-RT-KB917607-x64.msu