Changed TCP/IP settings revert after restart

G'day!

On our P2P n/w, upgraded file server from NT4 to XP Pro.
Had "hard" IP addresses but now want sys to assign dynamic
IP addresses. On IBM Thinkpad running W98 SE, when TCP/IP
changed to allow sys to assign IP address, the laptop
connects just fine but checking TCP/IP properties I find
that settings have reverted to old "hard" IP address.
Unless I make manual change after every restart, laptop
will not connect to n/w next time. Machine *insists* on
remembering the obsolete fixed IP address. Can any of you
suggest what is going on and how I can make changes to
TCP/IP properties "non-volatile"?

TIA,

Frank