Virtualbox Windows 7 safe mode

You could try to start the VM. While booting reset it and normally Windows 7 will asks you if you want to boot into the safemode or just start windows. Or you can try to catch the keyboard at the very beginning of the boot process (while the VM is in the virtual BIOS) an keep hitting F8, than you should also get the option to start into safe mode.

EDIT:

It has nothing to do with virtual box. The Windows 7 Enterprise Evaluation has a bug so the safe mode doesn't work. One solution could be the "safe mode with networking". (Source: https://social.technet.microsoft.com/Forums/windows/en-US/ef0e41cb-955b-4a29-9318-2c56a198d746/windows-7-enterprise-safe-mode-problems?forum=w7itproperf )

I have similar setup and forced safe mode with msconfig that resulted in the endless boot loop. I tried all other safe modes with no luck. Even if I selected the normal mode in F8 menu, the system tried to boot in the safe mode and failed. The solution in my case was to select the repair mode in F8 menu, enter login/password (default IEUser / Passw0rd!), select the command prompt option in the recovery menu and use these commands

bcdedit
bcdedit /deletevalue {default} safeboot

to reset msconfig settings ({default} is identifier of boot loader from the output of the first bcdedit command). This way the system became bootable.