XP or is it explorer 7?

I deal with quite a few banks that use enhanced security. In most cases to avoid answering a bunch of security questions, you register the computer you are using and all is well. Lately at least 2 of the banks ask my security questions each time I visit unless it is in the same day or I have rebooted. It?s like a cookie? Or something gets wiped out each time I shutdown & restart. Any ideas? I don?t remember changing anything recently that would allow this.