When you install Virtual Drumline 2.5, three very important .nkx files are placed on your hard disk. These are large container files that contain sample data necessary for your instruments to play back properly.
When loading an instrument, if you ever receive an error saying "missing samples" or "sample not found" it may mean your .nkx files are misplaced or may not have been properly copied to your hard disk. By default, these .nkx files are located in the Virtual Drumline 2.5 folder, alongside the Instruments, Documentation, and Multis folders.
The correct file sizes for the .nkx files are:
Virtual Drumline 2.5_001.nkx - 1.95 Gigabytes
Virtual Drumline 2.5_002.nkx - 1.96 Gigabytes
Virtual Drumline 2.5_003.nkx - 161.4 Megabytes
Virtual Drumline 2.5_info.nkx - 3.2 Megabytes
Note: you will probably also see corresponding .nkc files as well. Don't confuse these for the .nkx files. Leave them in place, but they'll be much smaller than the .nkx files.
If the file size of your .nkx files doesn't match the sizes stated above, your installation may not be complete and you should manually drag these .nkx files from the VDL installation DVD into your Virtual Drumline 2.5 folder.