Hello mel0526, welcome to NST
First thing to try is safe mode. As the computer is booting press F8 repeatedly until an advanced options boot menu appears. Select "Safe Mode" from there. If you can get into there, start typing "System Restore" in the search box of the start menu until it shows up and click on it. Restore the computer to a time prior to the update installing that caused problems.
Now if you can't get into safe mode, use your Vista DVD with the instructions stated here. You may also try system restore from that menu which may help.
First thing to try is safe mode. As the computer is booting press F8 repeatedly until an advanced options boot menu appears. Select "Safe Mode" from there. If you can get into there, start typing "System Restore" in the search box of the start menu until it shows up and click on it. Restore the computer to a time prior to the update installing that caused problems.
Now if you can't get into safe mode, use your Vista DVD with the instructions stated here. You may also try system restore from that menu which may help.