lan problems on startup

No network card detected on startup "sometimes"
Specs are Amd atholon 1045mhz
chipset is sis 735
windows 98se

Fellow worker asked me to look at his computer
because he couldn't get online.
I'm now typing this with his computer,my problem is that 70% of the time I restart this computer it will be online and the other
30% I have to pull the power cord out of the
back of the modem, wait about 2 seconds, and instantly it's detected.
I instantly thought IRQ conflicts, nothing detected in the device manager......I pulled out his pci modem card(communication device) that was sharing his same IRQ...same response...
Disabled his onboard modem also in the bios,
same response....
He has an onboard lan... My next step is to
disable is onboard lan and stick in a pci card. Is this the route I should try or am I on the
wrong track, any help would be appreciated!

P.S He had Window Me and he had three others looking at his computer and couldn't get online. I threw windows 98se on his comp.
wasn't that easy cause his cdrw(master)
couldn't read all the cd's but his dvd rom reads them all had to be switched around from
master to slave and slave to blah blah blah

 

I guess maybe I should of posted this in the Hardware
forum.
I disabled the onboard LAN and put in a NIC card and
everything is fine