If you had developed a VS 2005 project containing ADOX references on a Win XP machine and moved the project to a Vista machine, VS 2005 may not access to ADOX reference.
Then you'll need to use the "tlbimp.exe" (Type Library Importer) tool which is shipped with Visual Studio 2005 (full path is "\Microsoft Visual Studio 8\SDK\v2.0\Bin\TlbImp.exe") . Tlbimp.exe can convert the type definitions within a COM type library into equivalent definitions in a CLR assembly.
Here are the steps to get your VS2005 work on Vista :
1) Copy the "%Program Files%\Common Files\System\ado\msadox.dll" from working XP machine to Vista machine
2) Execute "tlbimp msadox.dll /output:MSADOXASM.dll" . This will create the CLR assembly file "MSADOXASM.dll"
3) Add this assembly to your project and add the "using MSADOXASM;" statement to your code.
4) The references will start working without issues