Recently, I am come across the issue where Dell OptiPlex 3010 was unable to load boot image using PXE boot successfully. System was unable to load boot.sdi file. Loading Files, File \SMSBoot\boot.sdi, WDS log shows the message "TFTP download failed". Resolution: This issue might occur if following registry entry added to SCCM Distribution Point with PXE. HKEY_LOCAL_MACHINE\ Software\Microsoft\SMS\DP\RamDiskTFTPBlockSize Type Reg_Dword Value: 16384 Dec (Do not use higher value than this!) Recommend that you increase this setting in multiples (4096, 8192, 16384, and so on) and that you not set a value higher than 16384. Please change the value of RamDiskTFTPBlockSize to 8192 or lower to resolve this issue.