BUG #7851: Installer crash with message: An error occured executing the Microsoft VC++ runtimeinstaller

The following bug has been logged on the website:

Bug reference: 7851
Logged by: ivano luberti
Email address: luberti(at)archicoop(dot)it
PostgreSQL version: 8.4.15
Operating system: Windows 7 Home Premium 64 bits
Description:

I know this is probalby a duplicate of bug BUG #7526 but I don't know how to
update it with new information so I submit a new one.
The same error message raised with 8.3.22 and 9.2.2.
But I was then able to install 8.3.22 using the pginstaller found at

http://www.postgresql.org/ftp/binary/v8.3.22/win32/

Ok this the new piece of information. Unfortunately pginstaller is available
only for 8.3.x. So I'm stuck since I need 8.4.x

The bitlog file provides the usual information:

Log started 02/05/2013 at 11:13:15
Preferred installation mode : qt
Trying to init installer in mode qt
Mode qt successfully initialized
Could not find registry key
HKEY_LOCAL_MACHINE\SOFTWARE\PostgreSQL\Installations\postgresql-8.4 Data
Directory. Setting variable iDataDirectory to empty value
Could not find registry key
HKEY_LOCAL_MACHINE\SOFTWARE\PostgreSQL\Installations\postgresql-8.4 Base
Directory. Setting variable iBaseDirectory to empty value
Could not find registry key
HKEY_LOCAL_MACHINE\SOFTWARE\PostgreSQL\Installations\postgresql-8.4 Service
ID. Setting variable iServiceName to empty value
Could not find registry key
HKEY_LOCAL_MACHINE\SOFTWARE\PostgreSQL\Installations\postgresql-8.4 Service
Account. Setting variable iServiceAccount to empty value
Could not find registry key
HKEY_LOCAL_MACHINE\SOFTWARE\PostgreSQL\Installations\postgresql-8.4 Super
User. Setting variable iSuperuser to empty value
Could not find registry key
HKEY_LOCAL_MACHINE\SOFTWARE\PostgreSQL\Installations\postgresql-8.4
Branding. Setting variable iBranding to empty value
Could not find registry key
HKEY_LOCAL_MACHINE\SOFTWARE\PostgreSQL\Installations\postgresql-8.4 Version.
Setting variable brandingVer to empty value
Could not find registry key
HKEY_LOCAL_MACHINE\SOFTWARE\PostgreSQL\Installations\postgresql-8.4
Shortcuts. Setting variable iShortcut to empty value
Could not find registry key
HKEY_LOCAL_MACHINE\SOFTWARE\PostgreSQL\Installations\postgresql-8.4
DisableStackBuilder. Setting variable iDisableStackBuilder to empty value
[11:13:19] Existing base directory:
[11:13:19] Existing data directory:
[11:13:19] Using branding: PostgreSQL 8.4
[11:13:19] Using Super User: postgres and Service Account: postgres
[11:13:19] Using Service Name: postgresql-8.4
Executing cscript //NoLogo
"C:\Users\luberti\AppData\Local\Temp\postgresql_installer\installruntimes.vbs"
"C:\Users\luberti\AppData\Local\Temp\postgresql_installer\vcredist_x86.exe"
Script exit code: 1

Script output:
Errore CScript: Impossibile trovare l'interprete di script "VBScript" per
lo script
"C:\Users\luberti\AppData\Local\Temp\postgresql_installer\installruntimes.vbs".

Script stderr:
Program ended with an error exit code

An error occured executing the Microsoft VC++ runtime installer.

I have already tried registering the vbscript.dll and checked the rights
(every user can read and execute it)

The TEMP and TMP variable are configured with default values:

C:\Users\luberti\AppData\Local\Temp

the users is the pc admninistratot

I have avira installed

I have tried with both windows firewall enabled and disabled

Don't knw what else to do.