Summary: Why can't I install Photo Gallery and Movie Maker?This is what an installation error should not look like:
An unknown error occurred. Error: 0x80096005 Source: D3DX9Thank your Microsoft, kids!
UPDATE: Okay, after getting a number of hints from troubleshooting posts, I was able to fix the problem. It looks like my system missed the original DirectX 9 DLL (D3DX9.DLL). I don't know why it's missing. Maybe some program removed it when it was not supposed to (I did not see any errors related to DirectX 9, though). So, I just made copies of the latest version of the DirectX 9 DLL (D3DX9_XX.DLL) in the System32 and SysWow64 folders and renamed the copies to D3DX9.DLL. Problem solved. Hope it helps someone.