Persistent malware?

[Andrew B.]

My computer was showing signs that it was infected. One being that something was turning off Malwarebytes monitoring and I was unable to turn it back on. Plus other flaky behavior.

So I did a factory refresh from DVD. I've done this before, and with no problems. But this time I had problems. I got problems early in the process. Trying to have it redo the partition led to an error message. I had to forego this and use a different choice on the menu. Then after I was all done I ran into problems. The provided Norton gave me an error message, told me to do this. With the last step being to run Norton Eraser, which looks for malware. It found none. And other symptoms, like slow Internet (per speedtest) and the there are no signs that Malwarebytes is running in the background. IOW, no tray icon, nothing in task manager. Manual scans by Norton and Malwarebytes show nothing.

Anyway, I'm wondering if something could be hiding in the master boot record, or somewhere else that allows it to persist? And how I can nuke this. I remember years ago under DOS I redid the MBR by using the undocumented fdisk/mbr. I'm wondering if there is something similar or better I can do. I realize this will wipe out my hard disk, but I don't have much installed right now. I just did this yesterday.