Low level formatting will wipe out a boot virus along with anything on the hard drive. You really don’t want to low-level format without the manufacturers recommendation. There’s a better way.
The Master Boot Record (MBR) basically tells the computer where its partitions and drives are, and then transfers control to the next sector to be read normally the boot record on a partition (like C:).
A virus moves the real MBR to slack space,” a sector normally unused by your computer. Then its puts its own rotten self where the Real McCoy belongs, so that all the partition information comes from a nasty source.
If the virus is in “Stealth” mode, a normal antivirus scan may not pick it up. The clever little creep may redirect the scanner to the right MBR (“see? Nothin’ wrong here!”) then will scan as normal even though it’s in the wrong place. It could also pre-empt all DOS calls to the file (“Hey! Virus scanner a ‘comin’!”), run ahead, and actually disinfect the MBR before it’s scanned. Then, when the call is over, the virus re-infects the file.
If you’re trying to boot to drive C: and you get an Invalid Drive Specification error—bingo, you’ve probably got a Master Boot Virus. A simple boot sector virus is more likely to give you a “General Failure Reading Drive C: error.
So now what? Breathe deep and do these things, on this order ;
1) Use a clean rescue disk (make sure it’s write-protected before you stick it in a potentially infected drive!) with current virus definitions on it. That should give you a clean boot to drive A:, which can then remove infection from inactive drive C:.
2) Get a rescue disk from a friend with a clean system, if yours doesn’t work. It’s possible you’ve had the virus longer than you realized.
3) Replace the MBR by booting clean (make yourself a boot floppy with system files and FDISK/MBR. This overwrites your infected MBR and puts a nice fresh on in the right place. You could probably do it by booting to the C: prompt, but it’s best to try to fix the virus when it hasn’t been activated. Stick with the clean boot floppy to be absolutely sure.
4) No luck getting rid of it? Hope all your data’s backed up! Reformat your hard drive, Which will not only write in a new MBR, but will add a new File Allocation Table. This means that it will basically tear out the Table of Contents on your computer and put in one that says your hard drive is blank. The data files are actually still there until they’re overwritten. Your computer (or the virus) just doesn’t know that.
You can get some useful information about viruses, and how to detect and get rid of them
at Quarterdeck and Symantec.
If you are still curious about low-level formatting, you can get a program from a company like Norton or from your hard drive manufacturer. Your BIOS may also have some hard disk utilities with the format option. Only use low-level format as a last resort.