Tosh McCaber
You need two network cards in your W98 machine (You haven't mentioned whether the BB connection is USB or to an ethernet card on the W98 machine - I have assumed ethernet) and the Mac needs an ethernet card configured for TCP/IP.
Then, enable ICS on the W98 PC. It will "auto-configure" itself as a DHCP host, and will allocate a private network address for the second ethernet adapter (on the W98 PC)
As mentioned above, you'll either need a hub or a crossover cable to connect the Mac and the PC.
If the Mac can get an IP address from a DHCP server, then always start the W98 machine first, so that the Mac gets an address.
If the Mac cannot get an IP address from DHCP you need to tell it what address to use:
The "default" private address ICS creates (on the 2nd card) will probably be 192.x.y.z which is a "class C" address.
Now set the Mac IP address to 192.x.y.q - where q is the only different number to the W98 machine.
Set the Mac netmask to 255.255.255.0
Set the Mac default route to 192.x.y.z
Bob's your uncle.
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Been using W98 and XP ICS for donkey's and have never (ever) had any issues. Shared amongst Mac/NT/UNIX and other (older) clients.
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The pinouts for crossover cables are: (just incase you felt like making your own

)
X-Over
1 Rx+ 3 Tx+
2 Rc- 6 Tx-
3 Tx+ 1 Rc+
6 Tx- 2 Rc-
And for a normal fly-lead:
Normal or Straight-thru
1 Tx+ 1 Rc+
2 Tx- 2 Rc-
3 Rc+ 3 Tx+
6 Rc- 6 Tx
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Bins, Bill Gates pumped $100M of his own dosh into Apple a few years back much to the dismay of people who always thought Microsoft were anti-Apple.