Setup failed while registering ISA Server filters

Problem: When installing ISA Server, the following error message is displayed:

Setup failed while registering Wspadmin.dll

Details:
The function My_LoadLibrary failed at the function Registrator::RegisterComControl

Cause:
This may occur when ISA Server 2004 is installed on a computer where a previous installation of one of the following programs was not completely removed:

 • Microsoft ISA Server 2004

 • Microsoft ISA Server 2000

 • Microsoft Proxy Server 2.0

Solution:
To resolve this issue, remove the remnants of the previous ISA Server installation or the previous Proxy Server installation, and then reinstall ISA Server 2004. To do this, follow these steps:

• Start Microsoft Windows Explorer.
  
• Remove the following folder if it exists:
  

%programfiles%:\Microsoft ISA Server

•  Locate the %WINDIR%\System32 folder, and then remove all the following files if they exist:
  
  • Cachctrs.h
    
  • Cachctrs.ini
    
  • Latui.dll
    
  • Mspapi.dll
    
  • Msfpc.dll
    
  • Msfpcui.dll
    
  • Msphlpr.dll
    
  • Msplog.dll
    
  • Mspmon.dll
    
  • Mspmsg.dll
    
  • Mspsec.dll
    
  • Mspui.dll
    
  • Pfctrs.h
    
  • Pfctrs.ini
    
  • Ratlib.dll
    
  • Msfpcstg.dll
    
  • W3papi.dll
    
  • W3pctrs.h
    
  • W3pctrs.ini
    
  • W3pmib.dll
    
  • Wspapi.dll
    
•  Run the ISA Server 2004 Setup program.