Windows 7 - Wont Start After Automatic Update

I've been trying out Windows 7RC on a spare PC thats about 4 years old with an AMD processor (XP3000+) & 1gb ram.

It's been running sweetly until I tried to start it last night and it wouldn't and it seems that it may be due to an automatic update that installed when I shut it down last. Not sure what the update was - I didn't even know it had one to install.

Well, it tries to start but keeps coming up with a "Windows Error Recovery" screen giving two options -

1) Launch Windows Recovery (Recommended) or
2) Start Windows Normally

..but the second option is greyed out and not available.

It then goes to another screen with a window titled "System Recovery Options" where you choose a keyboard layout. Then onto another "System Recovery Options" window with a choice of using recovery tools and picking an operating system (but none are mentioned) or restoring using a system image I had created earlier (but haven't).

Basically it seems that it doesn't recognize that it has an operating system at all.

Anyone have any ideas what's happened and if there is a solution (other than re-installing lol)?

Thanks.