Upgrade 98FE to XP, Modem sees pc as 98

I hope this goes to the right forum.
I upgraded my dad’s pc from 98fe to XP, which worked a treat, but now the BT broadband basic modem diagnostic tool still sees the pc as Windows 98 which is not supported. There is no info on Win98 in HKLM\Microsoft\Windows\CurrentVersion to point to Win98, so where else can it be getting this info? If you can help, that would be great!
Thanks, Harvey.