AlecStarr, please dont give advice on that which you know nothing about.
Malkosha, your problem is most likely a new "feature" called ForceGuest. You can get your security tab two ways: either hold CTRL while clicking Properties in the context menu or find the ForceGuest key in the reg and set it to 0, then reboot (this will revert the security model back to that of Win2k).
-W