I am not very technically-minded but this is my experience of being locked out of Win7.
A while ago I had exactly the same problem saying the user profile cannot be loaded. I had two profiles, one was Tilly with no Administrator authority with no password required, the other was OH with Administrator authority, with password. It was OH’s profile which could not be loaded. OH could still get to all his stuff through C>Users>Tilly but could not authorise any changes etc. Because of this, I Tilly couldn’t do any changes or alter my profile to add Admin authority to my profile. Took ages to read through tons of stuff online and eventually cracked it.
Can’t remember exactly what I did, but started with F8 into Safe Mode with Command, you don’t need password for this stage, just as smudwhisk stated. Activated the hidden built-in Admin account (plenty online which states exactly what to type but something like net user administrator /active:yes), reboot and a new Admin profile appears on the desktop and then through that profile I created a new profile with Admin rights. From that I amended the Tilly profile to also include Admin rights. Created a new OH profile with different name. Copied & pasted all old OH’s stuff over to new OH profile. Took a while but I wasn’t confident enough to tackle altering the Registry.
Even if you only have the one profile, you should be able to activate the hidden Admin profile from F8 Safe Mode with Command. If you do sort this out, make sure you make another (spare) profile with Admin rights, purely in case this happens again.
Good luck. It took me a few tries with F8 and also a few attempts to get the right message in the Command box.