1801-microcode patch error -missing or invalid processor microcod patch please contact compaq computer corporation For a new rom processor stepping Initializing intel (r) boot agent version 4-1-08 pxe 2.1 build 083 (w f m 2.0) r p l v2.74

SOURCE: "1801 Microcode patch error. Missing

http://h20000.www2.hp.com/bizsupport/TechSupport/SoftwareDescription.jsp?lang=en&cc=us&prodTypeId=12454&prodSeriesId=96295&prodNameId=97121&swEnvOID=1093&swLang=13&mode=2&taskId=135&swItem=PSG_I15378-37635

And follow the instructions here to upgrade the BIOS. I suggest using their instructions as they will be far more accurate than mine for this specific system and BIOS update.

SOURCE: 1801 microcode patch erro

These are very different CPU's, and you should make sure the board accepts the new one. Check the manual.