Re-start, press the relevant key to get into BIOS - change the boot sequence to boot from CD first, shut down the computer.
Re-start - insert CD when asked - continue. After the computer starts, run "System Restore" and restore to an earlier good date.
Back-up the system. This is a time consuming process and may take hours.
Now open Control Panel and attempt to run Updates by setting the Updates to Auto. (Sometimes the updates will be downloaded and installed during shutdown).