Problem Windows 7 DNG files

When downloading DNG files from my Pentax cameras it takes about 10 times as long as it should to download to the windows picture folder.The cpu goes to 100% and hard drive is constantly running.Same problem with cpu and hard drive when trying to view files.Using the Adobe codec,the one from windows made it worse.

Can download and view using Faststone without these problems but would like to use the windows program for initial viewing and deleting.