A company plans to upgrade a network server. Before proceeding with the upgrade， the HCL （Hardware Compatibility List） and hardware is checked and necessary backups and documentation are made.  
The existing 512 MB of SDRAM is replaced with 1024 MB. The 10 Mbps network card is replaced with a 10/100 PCI network card. When the server restarts， beeps sound and the server does not pass the POST.  Which of the following is the MOST likely cause of the problem？（）