virtualbox.org

Mine as well.

Failed to open a session for the virtual machine Windows 7 - School Use Only.

Could not open the medium '/Users/msalis1/VirtualBox VMs/Windows 7 - School Use Only/Windows 7 - School Use Only.vdi'.

VD: error VERR_FILE_NOT_FOUND opening image file '/Users/msalis1/VirtualBox VMs/Windows 7 - School Use Only/Windows 7 - School Use Only.vdi' (VERR_FILE_NOT_FOUND).

Result Code: NS_ERROR_FAILURE (0x80004005)
Component: Medium
Interface: IMedium {29989373-b111-4654-8493-2e1176cba890}

If nothing has changed, no sub-directories shifted, and no Host OS changes have occurred, then why am I getting this message?

Don't hijack other's people thread. I have split this from the one you posted under, as it had no relation whatsoever and is against the forum rules.

Well the error means exactly what it says : the file couldn't be found, in this case the VDI of the VM. So I would double check and triple check that the pack of the error message is valid.