Go into safe mode and see if that works. If it does check and see if SP3 was installed. If so you can uninstall it and see if that fixes it. If not I would just uninstall all the other updates. Better yet I would just reinstall windows. this time only load up the chipset and nic drivers. Install SP3 and all other updates. If you use an ATI card be sure to install at least .Net 2.0 for CCC, if you use it. Once the OS is patched and running right then install the other drivers that are left one at a time with a full reboot in between to make sure it still works correctly.