Registry Error - HELP ASAP!!

Hi all,
I need some help fast. I was working on a laptop for a guy. He brought it to me, and I found out that it had many viruses on it. I removed all of them, and installed a virus scanner for him. The laptop ran fine. I then ran my Windows Update CD. After it restarted, I got a blue screen that said Registry Error. Then the laptop rebooted. I tried Safe Mode - same thing happens. I tried to Load last known good configuration - same error. Lastly, I figured that I could repair the Windows Installation using the XP Home CD. Setup says that it can't find a previous version of Windows installed. Now, how, can I uninstall those security updates without being in Windows? How could I repair the registry? Or, what else can I try??

 

http://support.microsoft.com/default.aspx?scid=kb;en-us;307545

 

Well, this says, "Warning Do not use the procedure that is described in this article if your computer has an OEM-installed operating system." This computer had Windows installed on it from the factory. What else can I try???

 

Also, what if I don't know what the Administrator password is? How can I reset it?