As fast as the processor is and as large the amount of RAM you have installed, it doesn't necessarily mean that everything is going to happen in an instant.
Transfer of data between components is a bottleneck, the way Windows and software is configured can be another.
It sounds to me that there is a delay in the process of initially locating the file. This could be incorrectly configured drives causing a slowdown, but it's more likely to be a software cause.
Is Windows set to index files on the drive? If very large numbers of files are stored on a drive, Windows Indexing can actually slow down access, rather than speed it up! Are files compressed? That would cause a delay in access? Is antivirus software set to scan all files on access? Yet another slowdown.
You're never going to have file access occur instantaneously. The drive heads have to be moved to position from 'park' to access the file for starters. But the access times could certainly be improved, and you'll need to look at your software and settings to find what's slowing it down.