Hi Guys. I already found one explaination from Microsoft. But I still don't think it explained my all problem. http://support.microsoft.com/kb/927665/en-us According to this artical, The msdia80.dll should be under: driver: \Program Files\Common Files\Microsoft Shared\VC\msdia80.dll In my machine, I have 2 partition. In fact, in x64 OS, I can find 2 files. 1st one is under the D:\ The other one is in driver: \Program Files(x86)\Common Files\Microsoft Shared\VC\msdia80.dll So, according to MS site. I should also put the D:\msdia80.dll into this folder. driver: \Program Files\Common Files\Microsoft Shared\VC\msdia80.dll. My question is: Is this 2 gonna conflict with eachother? Or I should keep them both? driver: \Program Files\Common Files\Microsoft Shared\VC\msdia80.dll driver: \Program Files(x86)\Common Files\Microsoft Shared\VC\msdia80.dll Anyone could answer my problem? Please give me some hint! Thanks!