what is the iMac network card?

Have a look at the > iMac (Late 2006) - Technical Specifications

Look down the specification page to "Communications"

Built-in 54-Mbps AirPort Extreme Card (802.11g standard) (3)
Built-in Bluetooth 2.0+EDR (Enhanced Data Rate) module (1)
Built-in 10/100/1000 BASE-T Gigabit Ethernet (RJ-45 connector)
Works with 56K V.92 Apple USB Modem (sold separately)

17" iMac Intel Core Duo - 1.5GB Ram - Mac OS X (10.4.10) - Maxtor 300GB FireWire - Creative Inspire 2.1 - 2G Nano

There is no "card." It's all implemented on the logic board except for the Airport card and external modem.

Look at this Apple Bootcamp page down under "What you’ll need"

The drivers you need to come from Service Pack 2...

Have you been to The Apple Bootcamp Forum

17" iMac Intel Core Duo - 2GB Ram - Mac OS X (10.4.10) - Maxtor 300GB FireWire - Creative Inspire 2.1 - 2G Nano

All the drivers needed are included on the driver CD you burn when installing Windows via Boot Camp. Read the Boot Camp documentation.