Help!

I defragged my PC yesterday and today I get the following error

The following file is missing or corrupt,
\WINDOWS\SYSTEM32\CONFIG\SYSTEM

As the error message suggested, I booted using the original CD Rom and went into repair console. After several minutes it took me to the windows command prompt.

So, what do I do now?

I am desparate to preserve my date, emails etc. I do have a backup but it is slightly out of date.

Thanks

Howard