If you really want to hide your VL install, you could easily install LILO on a floppy or USB drive (assuming your machine has a floppy drive), and just dont write it to the MBR. That way, when you want to boot into Linux, pop the Floppy or USB drive in, and choose your OS. Your boss will never know there is a linux install there
Another option is to boot it with the Install cd
When the initial screen comes up, type
linux root=/dev/hdxx ro
Of course, replace hdxx with the address to your linux root partition.