If you bought it new, new as in from a major retailer vs eBay, then it did not have a virus. Your AV was giving you a false positive, something Norton does frequently.
There is no way for reformat it back to factory specs. Any type of formating you do will realign the clusters, create a MBR and create a partition table. Sorry.
"what can i do?"
You can learn that formating isn’t a cure for everything. 
