Can't load themes, getting error

Hello, I’m getting the following error when I try to load a theme
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Warning: touch() [function.touch]: Unable to create file D:\Inetpub\cascadeautoblog/wp-content/mymag.tmp because Permission denied in D:\Inetpub\cascadeautoblog\wp-admin\includes\file.php on line 199

Download failed. Could not create Temporary file.

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This is a new site and the first time I’ve tried to load a theme, is there some permissions setting I may be missing?

What do I need to change or modify to fix this.

Thank you

Lawrence