Windows 7: Getting rights to copy files off system disk connected via USB

Today my Windows 7 laptop wouldn't boot, returning a persistent Windows Boot Manager error 0xC00000e9. It recommended allowing Windows to start in a diagnostic state, which didn't help.

I pulled the hard drive and put it in a USB adapter which I plugged into another Windows 7 system. I was glad to see all the normal directories off the root. When I tried to change directories to \Users\Frank to copy off some critical files, it said I didn't have sufficient permission.

Can anyone help with what I need to do to accomplish this? I thought I was logged in as Administrator on the second system while examining the drive. Later I may try putting the drive back into my laptop and booting off a CD to try to repair the disk, but my highest priority is to get some critical files off the drive as soon as possible.

Update: I plugged the USB adapter with the system hard drive into a Macbook, and could copy out files from my Documents directories. However, I also wanted to get some email database files stored under \Users\Frank\AppData. Unfortunately, under \Users\Frank, AppData wasn't visible. I gather this is normally hidden. Is something different required to make it visible?