The 'Microsoft.ACE.OLEDB.12.0' provider is not registered error with Vista 64bit
If you're getting this error while trying to connect to Access 2007 or Excel 2007 via the Office 12 OleDB provider, you must first make sure you have the Office 2007 data providers installed.
Next, under x64 (64bit), the data providers will not work by default as they are 32-bit only (x86), even if the data providers download page doesn't say it. You have to explicitly compile for x86 instead of the default "Any CPU" platform:...