You could try setting the permissions for the root of your hard drive to Administrator can do everything (should already be this way), then tell it to set all child folders the same way. I forget what the exact steps to do this, but I had to do this before when I was messing with permissions settings and messed up. This will restore access hopefully. Making new accounts and copying info is up to you. Note that this may screw up the permissions on the current user folders...