Error Number: 0x800C0005 during install

Before delving deeper into registry settings and the like, make sure that if you are running Windows Vista or Windows 7 you run the setup installer AS ADMINISTRATOR (right-click on it choose "Run as Administrator").

If that doesn't work:

Information from Microsoft:

This behavior may occur if certain dynamic-link library files (.dll files) are not registered correctly or if there is a firewall between the computer and the Internet that does not allow HTTPS (SSL) connections. RESOLUTION

To resolve this behavior, use the regsvr32 command to reregister several .dll files:

1. Click Start, click Run (or just type into the search bar in Vista), type cmd in the Open box, and then click OK.
2. At the command prompt, type the following commands. Press ENTER after each line:

   regsvr32 Softpub.dll

   regsvr32 Wintrust.dll

   regsvr32 Initpki.dll

3. Click OK.
4. Restart your computer.

Some have reported that simply re-registering the MSXML3.DLL seems to fix the problem.

1. Click Start.
2. Choose Run.
3. In the Run box, type:

   regsvr32 MSXML3.DLL

4. Press okay

If that hasn't helped you may need to re-registered some more files:

1. Click Start.
2. Choose Run.
3. In the Run box, type (pressing okay after each one) :-

   net stop wuauserv

   regsvr32 wuapi.dll

   regsvr32 wups.dll

   regsvr32 wuaueng.dll

   regsvr32 wuaueng1.dll

   regsvr32 wucltui.dll

   regsvr32 wuweb.dll

   regsvr32 MSXML3.dll

   regsvr32 qmgr.dll

   regsvr32 qmgrprxy.dll

   regsvr32 jscript.dll

   net start wuauserv