Right. While dual booting, the Windows 7 HDD should show up in the Dolphin Explorer. From there you can explore all the files located in that partition (copy/rename/overwrite etc). Though by "keeping it secure" is a little vague by what you mean? However, if you use your windows 7, seeing the files in Kali partition takes a little extra work (the files system is not natively supported - thus doesn't show up in windows explorer) .
Fact, Science and the Pursuit of Knowledge. Working to secure your networks from threats; Outside and Within.