Usually the easiest files to move are your data files, since they don't require any special configuration after they're moved. Programs might work too, but it's probably easier to reinstall them on the D drive rather than manually moving them, because they'll be expecting files in the wrong spots.
To move files in Windows Explorer, simply drag and drop the files from the C drive to the D drive. This will copy them, not move them, so once the copy is completed, you can delete the old copy that exists on the C drive.
Hope this helps
John A
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