A cardbus adapter is any device which slides into the PCMCIA slot on the side of a laptop computer to provide a particular functionality or connectivity in addition to whatever is already built into that system by the manufacturer. In your specific case, it appears that the sales agent is recommending a certain compatible wireless adaptor card but using the generic term "cardbus adapter." With wireless equipment, despite the so-called standards, there is a lot a variation and incompatibility between different brands and even between different lines of the same brand. If you want the D-Link Xtreme G router, you will likely have fewer headaches if you use D-Link Xtreme G client adapters in your computers.
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I am very new to wireless routers, and I am planning to buy D-link Xtreme G DI624 wireless router, but at the store they told me I have to buy a cardbus adaptor for 59$, so What is the cardbus adaptor ?? and Should I buy it or it is NOT IMPORTANT ???

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