You will have to select in BIOS to use the integrated chip, though I think that most systems will recognize and use the PCI card.
Also, make sure to completely delete the drivers for the HD4200. I don't know if graphics drivers for discrete and non-discrete GPUs operate the same, but make sure it's cleared.
Well I'd be doing a complete resintall of my OS, so drivers wouldn't be an issue. I just recall hearing something about certain features don't work if you mix nVidia and ATI, but I might just be going crazy.