Startup hangs after installing Windows patches

Hello all,

I've just installed three Windows patches using Windows Update, and now my
machine will not complete the startup - it hangs with an hourglass, and C-A-D
allows restart. Any ideas on what I can do to try to fix this?

Many thanks,

The hang appears to be near the end of the startup - antivirus is started,
and there are various normal items showing in the right of the Start bar.

I didn't note which fixes were installed, but I think two were Windows and
one was Internet Explorer.

So far, based on items on this forum, I've tried:
Running anti-virus in safe mode
Checking device manager for obvious problems
Removing the ethernet cable to broadband