freaky lan- inet connection

[corosus]

i've got this friend who is working on a old pentium 1 100mhrz of mine every iternet conecting aplication work fine, but as said before it's just a p100.
i've had this 233 lying around and i gave it to her and installed it, but the internet connection is freaky.
it works, slowly, sometimes
both pc's are win98se. all network settings are set to automatic, and everything is identical when using the winipcfg command, exept that the ip adress is 192.168.1.100 on the old one, where the intrernet works, and itts 192.168.1.101 on the one where it does not work and the lease... says an exacte date on the on the pc where the inet is wierd and it says "DD:mm:03 14:10" where the inet does not work.
i've tryed to reinstal the nic and the tcp/ip protocol, this did not help.
the NIC and network are fine (i can ping myself)

this is a realy wierd problem, please help