I am unable to open Sony Vegas Pro 9

The other day I installed Sony Vegas Pro 9 into my computer which uses Windows 7 64-bit version. When I tried to open it, it brought the error message below.
So I decided to confirm whether the Twain_32.dll file was in the Windows folder of my hard drive and confirmed that it was.
So I don’t understand what the problem is.
My WIA service is also activated.
Can anyone help?

Vegas Pro
An error occurred starting Vegas Pro.
The TWAIN manager could not be initialized. TWAIN_32.dll missing or corrupt.
