When I ran mbr.exe it gave me an immediate black screen then my computer auto-rebooted. Is that normal? What exactly did it do to my computer, if anything?
The programme runs under a command prompt, hence the black box/screen. Replacement of the MBR will require an immediate reboot to ensure safety
Should I have run it in the avast sandbox, as I was advised to do by avast, or outside of the sandbox? Is that what caused the black screen and autoreboot?
No MBR ran the routines - but as it was in a sandbox no changes were made
Maybe I shouldn't be running it at all, and I don't plan to run it again, but I'd like to know what happened, and why. Apparently a lot of folks are running it these days without knowing the consequences. Give a monkey a banana and he'll eat it.
Tell me about it, the amount of systems I see where the user has tried programmes that were found on the net and then wondered why the system did not work anymore. For the majority of infections I would recommend getting help on a reputable forum