I have a customer's computer that I have been working on for a couple of days. When I first turned to computer on, he had a fake alert virus that was claiming that all of his EXE files were infected - so they would not run. Not a problem, I ran The Killer to kill all the non-windows processes then ran Malwarebytes and Superantispyware. Malwarebytes picked up some trojans and some other malware, and Superantispyware showed a lot of tracking cookies. I rebooted and was thinking about what else I wanted to do to assure myself that the machine was clean. It was late; I quit for the night and left the computer running. In the AM I went to the machine to run the Eset Online scanner and found that the computer now had the FBI virus. As far as I can tell, it was there but masked by the fake alert. I did no browsing or anything else on that computer, and no other computer in the shop had the infection (except another one that I was working on).
The computer in question is running XP Pro SP3. I have tried Microsoft Defender Offline and AVG Rescue CD. I rewrote the MBR and the bootsector using a Windows installation disk.
I can't boot from Hitman Pro Kicksart from the USB or from a CD. The error message is "NTDetect failed". I did manage to start Windows using Hitman's option 3 (Legacy), which just boots from the hard drive. Hitman ran and found and fixed some problems, but the FBI virus was still there.
I am able to boot to a Hiren CD, but the options are fairly limited once the Mini XP OS is running.
What can I do now to eliminate this virus?