A few questions about your setup:
1. Are NIC's (Network Interface Cards) installed in both PC's?
2. Do both PC's connect to the NTL Broadband feed?
3. How do the PC's connect to the NTL Broadband feed (router, hub, modem...?)
4. Are Firewalls installed on both PC's? If "yes" please provide product name and version.
5. Will you be able to connect the PC's by Ethernet or do you need a Wireless connection?
6. Do the two PC's share common periferals (printer, scanner....)?
7. Which version of XP is installed Home or Pro and which service pack is installed?
8. Is 98SE up-to-date with all updates and service packs?