Since W98 has no inherant support for wireless networking,
you'll need to ensure whatever adapter you buy for it has
support/drivers for Win98.
It *may* be better to connect it to a wifi router (should
you decide to go that way) via standard network cable, and
just Wifi the XP pc's.

P.

Hi Sunny Side: the configuration you propose will put you over to the Dark Side as 98 has n't got built in Internet Connection Sharing and you'll have to buy Wingate softeware to allow the XP machine to connect.

Setup an XP machine as the 'gateway' and this all works like magic.

OK you have thew XP PC connected to the internet and now you want other PCs to share the internet access.  

Hopefully you’ll have Cable or DSL internet access.  Makes no difference to wireless LAN, but some places just can't get Cable Access [by the way Cable is of course many times faster].

What should one do?

First, make sure everything you buy conforms to the dominant wireless standard known as 802.11b, or Wi-Fi (short for wireless fidelity). That way you can mix brands, operating systems, even network a Mac to a Windows PC and everything should still work together.

There are two new, faster versions of Wi-Fi: 802.11a and 802.11g. "A" is for business use; "g" is for the home. Both bump networking speeds up from 11 megabits per second to 54 mbps. But unless you're moving around big video files or sharing other graphics-rich multimedia applications, "b" will be more than sufficient.

The heart of your network will be a wireless access point and the Internet Access or preferably one device that does both called a router, acting as Wireless Access Point and  cable or DSL modem and Network Switch. The two-in-one units, available from Linksys, D-Link, Netgear and others, start at about $100; with a few Ethernet ports and USB port too, so you can connect to PCs using a standard Ethernet cable or USB cable.

To establish a wireless connection between a desktop PC and the wireless router, you need a USB or Ethernet Cable.

To connect a notebook PC, you'll need a wireless PC card.  If new notebooks have Wi-Fi capabilities built in. Notebooks with Intel's new Centrino chip, for example, are Wi-Fi-enabled.  

Note that 802.11g is backwards compatible with 802.11b — meaning a laptop with a "g" card will talk to a "b" router, albeit at the slower speed — but 802.11a is not. If your office installs an 802.11a network, get a dual-band wireless PC card for your laptop so that it can connect both at home and at work.

Make sure that the software that comes with your gear will walk you through the installation. The steps will vary slightly, depending on each computer's operating system. The older the OS, the trickier it can be; Windows XP is designed to detect and configure a PC card to talk to an existing network.

Before you start, gather the following information:
•    your broadband connection's IP address, e.g., 123.43.2.1
•    subnet mask, e.g., 255.255.122.0
•    default gateway e.g., 192.168.0.2
•    DNS IP addresses e.g., 123.123.123.1
You can get these things from your Internet provider; your customer-service rep will know what you're talking about (or you can find this using the Properties tab, under Network Connections). Each is just a series of numbers (e.g., 123.43.2.1) that you'll be prompted to plug in during setup. (If your provider supports a protocol called DHCP, your router should retrieve these settings automatically when you plug it in.)

You may also be asked to choose an SSID (service set identifier) I recommend that you do not accept the default setting as anyone nearby with a wireless device can also use your internet access.  Set your SSID to a meaningful name use your Business Name.  For work-group name use ‘Wireless’  and a wireless channel select from 1 – 11, I recommend you use a higher channel as default settings usually select the lower end.  Keep these consistent for all of your machines.

Security
For additional security you can and should use Wired Equivalent Privacy (WEP) algorithm: and set this at 64bit: you can then choose a combination of 10 hexadecimal characters [0-9 + A-F], again for this may I recommend you select your mobile phone number as it is 10 characters long and not known to all your neighbours.

Additionally you can set the Access Point to only allow access to specific units, where you would enter their MAC address, again a series of Hex numbers, usually found on the Wireless Card plugged into the Laptops or other desktop PCs.