The virus warning didn't appear in Mint 16 on the same PC. It showed up immediately after I installed Mint 17 RC. It appears on a desktop PC (home-built, older AMD Phenom quad processor) but not in an identical install on a ThinkPad X201 laptop.BootSector Write !!
VIRUS: Continue (Y/N)?
I found the following reference to this on another forum:
So is this a Mint 17 RC bug? Haven't found a way to turn off the message.The motherboard is telling you that something wants to write to the boot sector. The boot sector is rarely written to but a virus would find it very handy to do that. An example of a valid write might be when you are installing a dual boot to Linux.
FOLLOWUP: A bit more research suggests this is a common issue that very often only indicates something other than a virus is trying to write to the boot sector. The solution suggested is to turn off virus checking in the BIOS, which is what I did, and Mint and Win7 boot now boot normally.