EDIT: I no longer have a problem, Windows is running properly, but just in case anyone else has the same experience I'll tell you what I did.
Having written the post below, I tried the "switch off with the button on the front" method. After a few seconds I powered back on and got the "Windows didn't shut down properly" non-Windows message.
I was then given the option to repair potentially damaged files, or start Windows normally. Knowing that a bloke on another forum had unsuccessfully tried the 'repair' option for this exact same fault, I tried the 'Start normally' option.
During start up I got the 'Applying update operation 217 of 217 (\Registry\Machine\Components\...)' message again for about two seconds, but then a Windows screen was displayed with the message "Preparing to configure Windows". This was displayed for a few minutes, then everything started as normal, albeit a little more slowly than usual.
Hope this is helpful to someone!! 
ORIGINAL POST:
Hi, last night 3 updates were automatically installed...this evening when we started our PC (OS: W7 Home Premium 64 bit) we got the following message on the Windows splash screen:
'Applying update operation 217 of 217 (\Registry\Machine\Components\...)'
It's now sat on that screen and apparently doing nothing. Someone else on the Windows 7 forum also has the same problem, and he used Windows System Restore, but no solution yet. Presumably if I system restore it, I'll just get the updates again wanting to install when I shut the PC down tonight.
Any ideas what I need to do??
Cheers.