Blaster Virus

In scenarios like you mention, to eliminate the
possibility of blaster, or a similar virus causing the
problems, I would download the stinger program from
Mcaffee. This is a small executable that will check for
approx 44 virus/worms/trojans, and remove from your
system. I have successfully downloaded this from infected
machines, although it does take a little longer due to the
excess of network traffic that such worms create.