Forgotten password on Vista Home Premium

Hello, I have one lap top with Vista Home Premium, but people can't guess that passswords on accounts.

I'm trying to reset/remove that pass.
I tryed with Offline pass remover, Ophcrack but no sucsess.

Also when I try to reset password on device(usb) it says that that's not a device for pass. backup.

Can someone help me to reset it ? They live in Italy and here are for a week.
They have only Guest account, there is no Administrator account.

Tryed to boot on safe mode, but there is no admin acc.

Someone to help ?

Thanks, Boshko.

Hello John. Yes, I tryed up to 3th method, and didn't work. I can't restore password on usb, I don't know why.

For the next, I don't have any recovery dvd's.( I guess that they are in Italy).