DHCP won't activate

Dell Dimension 4500, OS = XP Home. Could not connect to Internet automatically so set fixed IP address etc. and connected OK. Was loaded with spyware most of which I removed, updated BIOS. Discovered Cnet ethernet adapter had a problem. Link indicator light was on even when computer was off and no cable connected. Replaced with new D-Link adapter, but still couldn't connect to net without manual IP setting. Used fdisk to reformat HDD then reinstalled OS from recovery disks. Still must set IP manually. The AIPA is working as the auto IP starts with 169.254.x.y. Anybody got any ideas where to look. I suspect the bad adapter damaged some circuit on motherboard. Yes, I tried the new adapter in all sockets, to no avail. USB adapter and wireless adapters both USB and PCI also do not auto IP. Error message is always can't find DHCP server. Have 6 other computers on this net with no problems connecting.
(I no longer have this computer just looking for ideas, just in case)

 

What is the subnet for the 5 other pcs?

 

There is no specific subnet. The mask is 255.255.255.0, but to eliminate any net problems I disconnected all other machines and connected the problem machine directly to the DSL modem which in this case is the DHCP server. Still had the same problem.

 

I may have clicked the wrong reply button, just in case here is my reply.

There is no specific subnet. The mask is 255.255.255.0, but to eliminate any net problems I disconnected all other machines and connected the problem machine directly to the DSL modem which in this case is the DHCP server. Still had the same problem.

 

I'll go with you on the bad adapter idea, if you plugged that single unit into the router and could not get an IP - things look that way. Did you reset the router when you plugged that single pc in? (so the DHCP would clear out)

 

Thanks for the help, yes I reset everything everytime any change was made to insure that all started fresh.

 

I assume you've checked to see if your DHCP server is running in services? After the reinstall is should have been set to automatic, but never know.

 

The problem is beginning to surface. Two of my otherwise OK machines suddenly started having the same problem as original machine. Disconnected VOIP router which seemed to clear the problem temporarily. Then it returned a few hours later.
Opened the DSL modem and discovered the 169.254.x.y address was assigned as an LAN address. Did a software reboot on the modem and everything went back to normal (had power cycled it several times - no help) If problem returns the modem is going to scrap heap!!! (hazardous, that is!)