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He has a desktop computer so a wireless card would be necessary along with a wireless router.
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Not necessarily. First off, if you get a Linksys wireless router you'll have four wired ports on the back. If you can get his desktop within 100 feet or so, you can just tack CAT5 cable along the wall and you're good.
Or, you can get a wireless adapter instead of opening the case and putting in a WiFi PCI card. Amazon has one for under $50, and there is a $10 rebate available.
linky