IIRC you may have had a .net account created. If this is the case, go to "Start", "Control Panel" and "User Accounts". Just delete the extra user account.
If you get a screen that shows boxes instead of the "picture" login, you may have installed PCAnywhere pre-10.5. Those versions install an old GINA, and then you end up there; if that's the case.. bah, uninstall it, install SP1 again, and only install PCA10.5 or higher