in safemode open the run dialog and then type msconfig. disable every single service and startup program under the services and startup tabs. then restart and see if it comes up, if it does then go to services and enable all, check the box that says hide microsoft services. then disable the new shorter list and restart. if it comes up then you know its a 3rd party program causing the issue, if it doesnot then its a windows service or a driver and we can go from there.