Same issue...
Blind Dragon, I hope you can help me as well...
I had the same thing happen to me last night - no task manager, wallpaper changed to the same yellow text, auto-shutdown process, etc.
I tried to follow through your instructions, and I was able to install SAS and clean up like four hundred-something files and the SDFix (also had no "Y" option so I also did option 2 which downloaded some Norman utility) but for some reason the Anti-Malware program you recommended in your first instructional will not install. I used another comp in our house to DL the progs to a microSD and then moved them to my infected PC. I could install SAS and SD no problem, but when I click the mbam, I get nothing.
I'm so sorry to put you through this again, and thank you in advance for any help you might be able to give me.