I amended your header and thanks for posting.
Easy when you know what it is and how
When confronted with a computer with no task bar, no windows key to get to programmes.
No internet connection
No restore points & last good configuration
All your thinking about is backing up urgent data - no copy paste, no drag and drop and no why to get data off
Yes I do back up ... to separate usb hard drive.
I'm now £70 out of pocket getting this fixed. When I was able to get my hands on a computer to get to the internet I WAS WISE !!
But tell me that yesterday morning and PC World.
In order to have fixed my own computer I would have required the KNOWLEDGE AND access to the internet.
If there is an empty screen , try cntrl alt del, or right mouseclick in the bottom row, to get into task manager, and in application sgo to new task and type explorer or explorer.exe
This will bring the desktop often back.I found there was a problem with Mcafee when I saw the news on internet, Then I typed in google: update mcafee and found supposed solutions which did not help me, I found the above solution, which solved the problems ( no internet, no way of running programs, no way of installing or de-installing programs) .
If there are still thousands of pc's not working they should try the solution that worked for me (XP professional servicepack 3, , mcafee total protection)
So broadcast it further
So start up in safe mode
Copy back scvhost.exe to c:\programs files\system32
Restart in safe mode, remove mcafee, and install it again