WinXP Home fails to boot after Microsoft Windows Update

This is a dual boot machine with XP on a 150g Raptor and Vista Ultimate on a 120g Caviar. All was fine until Microsoft presented me with about 6 or 7 updates-all at once, while in WinXP. I unchecked one that had to do with Outlook, as I don't use it. The others were just WinXP updates, and there was a cumulative update for IE8.
I installed them and rebooted. I couldn't get into XP, but could still get to Vista.
I was later able to get into XP and tried system restore to a date earlier in the month. It looked like it ran(progress bar) to around 40% and then sat there for about 10 to 15 minutes with no further growth of the progress bar. I rebooted and tried getting into safe mode. I got the safe mode black screen, and the mouse cursor, but nothing beyond that.
I then booted into Vista, accessed the 150g Raptor, and under tools, ran the disk check with the fix as you go option checked. It stated that it fixed some errors, and told me where to find them.
I rebooted into XP, got as far as the desktop, without any icons or taskbar, and the following popups occurred:
Explorer.EXE-Application Error "The application failed to initialize properly
(0xc0000005). Click ok to terminate the application" When I clicked ok, I got the following: GoogleUpdate.exe-Bad Image "The application or DLL C:\Windows\System32\winhttp.dll is not a valid Windows image. Please check this against your installation diskette ". Clicking ok brings up the very same Explorer.EXE error and statement, as before. Clicking ok again , the desktop background remains-the harddrive churns away audibly(the Raptor has a distinctive sound when compared to the Caviar)-and another popup regarding Google( not the same one) comes up. Clicking ok then results in the desktop background with no icons nor taskbar, some harddrive activity, but no progress. The mouse cursor is visible, but left or right clicking does nothing.
Ctrl-alt-delete brings up the task manager with no tasks running. I can then click shutdown and click on shutdown to shut off the computer.

 

I got the exact same error message: failed to initialize(0xc0000005).
Thanks for the reply, Steve.