It is not possible to set a "default' directory for the <input type='file' /> html element, this is restriction by the browsers and there is no way to workaround it. Since RadUpload is based on the input type='file' element, it inherits this behavior. I suppose that this restriction makes sense since there is no guarantee that the folder set as default for the upload will exist on the given client.
With respect to your second question, the input will automatically remember which was the last opened folder. However, this behavior might differ under the different browsers.
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