Many applications make use of the ActiveX component WinHttpRequest for accessing web pages programmatically. On Windows Server 2008, these applications will get an "unable to load type library" when using ProgID "WinHttp.WinHttpRequest.5.1".

WinHttp is installed on Windows 2008 Server. The problem is that it is incorrectly registered; it uses a path name that requires expansion with the REG_SZ data type. Either the data type should be REG_EXPAND_SZ, or the data should be changed to an absolute path that does not require expansion. (I believe this was the state of affairs under Windows XP / Server 2003).

In a freshly installed Windows Server 2008 SP2 system, the relevant registry key is as follows:

Name=HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{662901FC-6951-4854-9EB2-D9A2570F2B2E}\5.1\0\win32=%SystemRoot%\system32\winhttp.dll

Type=REG_SZ

Data=%SystemRoot%\system32\winhttp.dll

The Type is incorrect; it should be type REG_EXPAND_SZ or an absolute path.

The component can be corrected by re-registering WinHttp using the following command (as an elevated user): regsvr32 %SystemRoot%\system32\winhttp.dll . After re-registering the component, the relevant registry key is:

Name=HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{662901FC-6951-4854-9EB2-D9A2570F2B2E}\5.1\0\win32

Type=REG_SZ

Data=C:\Windows\system32\winhttp.dll

After re-registering, WinHttp type libraries work as expected.