The stock install can give you the boot to either OS but for what you want, it's not a stock install and you should jump into the Ubuntu forums to ask if anyone has a ready to use install procedure to do exactly what you want.
Defrag in Windows should not touch the other file system so I would be guessing why the odd install or feature request.
I am trying to install Ubuntu on my family's PC but I want to hide that partition, so i can only access it by going to the boot menu in BIOS. I want the computer to single-boot so it goes straight into windows, as if the hidden partition wasn't there. The computer does get defraged so I want it to be hidden there also.
Is it possible?