I have ran into an issue with my SCCM 2007 R3 lab environment. I started off with an one client and a sccm windows server and everything seems to be working fine. I can PXE-Boot, sccm sees the computer, and I can send advertisements. However when I went to setup another client in the environment it is failing to PXE-Boot. In SCCM it sees both computers and the status for both are identical, I have firewall turned off on all machines. The computer is getting an IP address from the DHCP and I was able to join the lab domain(so network connection is fine). However the error that I get when trying to PXE Boot is;
PXE-E51: No DHCP or ProxyDHCP offers were received.
PXE-M0F: Exiting Intel Boot Agent
I have the computer in the same collection as the first computer and the advertisement has an os install task sequence advertisement configured. The first PC is getting an IP address and booting to the sccm utility so its not an advertisement issue. I also have enabled unknown computer support and I'm responding to all requests. I checked the BIOS setting for the PC and it is correctly configured with the network boot option with PXE. I have deleteed the computer and readded it into sccm. I have ran all of the actions from the configuration manager on the client. The only difference in the two machines is the model, PC1=Dell Optiplex GX620 and PC2(bad)= Dell Optiplex 780. Any ideas? Please help I have run out of them.