When you start Windows Explorer, by default it shows the 'my documents' folder and subfolders. If you do not have a folder pane on the left side of the window, click on the View menu, then under 'Explorer Bar' click 'Folders'.
In the folder pane, you should see 'my computer' listed under 'my documents' and its subfolders, with a plus sign on the left. Click on that plus sign and you will get a list of all the drives on your computer. Click on the plus sign next to 'local disk (C:)' (the name may be different, but it will be the c: drive), to see a list of folders. Next, click on the plus sign next to 'program files'; at this point Windows may pop up a warning saying this folder contains system files that are hidden by default, then ask if you want to unhide them, which you do. In the same way, you need to expand the subfolders under the 'Divine Divinity' and then 'run' folders, until finally the 'dynamic' folder is listed.
If click on a folder (or drive) in the left folder pane, Windows Explorer will display a list of all the files and subfolders that it contains in the right pane. You can double click on a folder there to move into that subfolder and show its contents, so could drill down to the required folder this way rather than clicking on the plus signs (though it may be a little slower if any of the folders contain a lot of files).
Anyway, once you select the dynamic folder in the left pane, it will display all of the files it contains in the right pane. Click the first file in the list, the scroll down to the end, press the shift button, and click on the last file, then hit delete. Alternately, you can click on any file and hit Ctrl-A (the 'select all' hotkey) to delete them.
With the 'run' folder expanded, you should also see the 'savegames' folder. To copy a folder to another drive you would just have to select it then drag and drop with your mouse. If you wanted to copy a folder to another location on the same drive, you would still drag and drop, but holding the ctrl key down to force a copy (default for drag and drop on the same drive is to move). There will be a + sign next to the cursor when copying, and no sign when moving.
