press ctrl+alt+del
click processes tab
end the process msblast.exe
This will stop blaster running. So you can now go online without it shutting your net connection down.
While online download a decent antivirus and the msblaster patch from microsoft
Then use the Antivirus to remove the infection.
you can get stinger here http://vil.nai.com/vil/stinger/
but this is not a full antivirus it just removes common viruses