I think probably the only reason the stipulate 98SE might be the USB support is poor, but as Skyver says if you have a Network Interface Card (NIC) installed you won't have a problem, but don't use the USB port because you may have problems, not saying you will, but the NIC is better.
As a matter of interest I'm on NTL and they say the same, but my operating system is Xandros Linux and I've never had a problem, even when I had to re-register my connecting with them when the connection was upgraded, I just opened the first available browser, in my case Opera, it connected to the registration page where I entered my details and away it went.
I can't even use the CD they supply because it doesn't work on Linux, so you don't even need that.
If you have a desktop Cable modem and an Ethernet port then you can just plug the modem in, wait 10 seconds and then you are ready to go. never used the CD after the engineer installed the modem the first time.
NTL however will make you jump through loops running the CD, verifying who you are etc even though the service arrives down a dedicated cable in to the room you had the cable run to.