Desktop permissions

Every time I drag an attachment from an email to the desktop and try to access it from within Parallels running Win 7, I get a permissions error. According to Get Info on the dragged file, read/write permissions are for me only with everyone having "no access".

I know I can access the file from Parallels/Win 7 if I manually set the everyone permissions to read/write. Is there a way to change the default permissions for a file dragged to the desktop to be read/write for everyone?