From the above linked site:
Create a subfolder in the "sysprep" directory, and name it "drivers". In here, you'll put all necessary drivers for the computers you intend the image to be used on. It may be wise to organize the drivers by i.e. make and model, or hardware type (Networking, Display etc).
REMEMBER: Most drivers, when downloaded, are a bundled archive of some sort. You have to extract the actual driver files - sysprep will not do this for you. I've often used WinRAR for this.
When done, you should have a neat folder structure under "C:\sysprep\drivers" containing all the drivers you need for your PC's.
Note the emphasis. That one is the single most common problem.
The next one is not including the chipset drivers.
Finally, another common mistake is to use very long names for the nested directories to the point that they exceed the maximum path length (1024 characters).