The Type II "PC Card" slot should take either the older 16-bit PCMCIA cards or 32-bit CardBus cards. For Wireless Networking, the laptop will need to be running 98SE or later.
If considering an 802.11g USB adapter, be aware that a USB 1.1 port will limit its performance to the 12Mbps speed supported by USB 1.1
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If you install a "g" WiFi adapter, it will perform in accordance with the 802.11g networking protocol - generally connecting at 54Mbps in an "Infrastructure" network and at 11Mbps in an "Ad Hoc" network.