It works *exactly* like that. Steps to set it up like that:
1) Partition HD. I suggest a 10/9/1 ratio, 10 being Windows, 9 Being Linux, and 1 being Linux Swap (type 82)
2) Install Windows, yadayada, ignore bad partitions.
3) Install Linux. Slackware installer will give you the option to install "LILO". Pick the MBR (master boot record).
Please note that installing LILO in the boot sector "could be dangerous", but we're asuming you have nothing important you can lose, as you just repartitioned your hard drive. If you do, you'd be best tossing it on a floppy disk (doesn't always work right, meh.)
Then, when you start your computer, LILO, in its wonderful black and redness, asks you to boot into Windows or Linux. (pick one).