Final answer:
The command FIXMBR is the correct choice to run after a virus removal if the computer will not boot, as it repairs the master boot record, which is crucial for booting the operating system.
Step-by-step explanation:
After a virus removal, if a computer will not boot, the command that may need to be run is FIXMBR. The FIXMBR command is used to repair the master boot record (MBR) of the bootable partition. Issues with the MBR can prevent the operating system from starting because it contains the information required by the BIOS to load the system.
Whereas commands like SCANDSK, which is a typo for CHKDSK (Check Disk), are used to check the integrity of the file system on a disk, DXDIAG is a tool used to diagnose issues with DirectX functionality, and MSCONFIG is used for system configuration and troubleshooting software conflicts.