If you're running Snow Leopard, just put in the install DVD.
Windows will see it as a driver install program.
If you're using Lion, launch Boot Camp Assistant, and select "Download Support Software."
Burn it to a CD or save to a USB drive.
Boot into Windows and use the drivers.
I do not believe you can simply download the drivers from Apple.
You could try running Windows update and get the latest drivers from Microsoft. Windows doesn't know you're on a Mac, i just knows it's an INTEL processor, etc..