i have this exact same problem and norton, trojan remover, all find nothing
ive ran ad aware and there was something about a possible virus so i removed that one and the problem still exsists.
ive used that Bazooka Spyware scanner and all that shows up is a Media Player GUI or something about how my media player could be snding infromation and all this crap but i really dont think thats whats causing the problem,

i raelly hope someone finds a solution to this because its not pleseant when i start up and dos screens pop everywhere saying "installing..."

thanks in advance