Installing new memory

[MichaelHany]

The system comes with 4 gb ram and i have 2 old ddr3 rams 2gb each i want to use them but the system doesn't read them probably due to low frequency can i make the system recognize these rams ?
Ram that came into pc are PC3-12800 (800MHz)
my old rams are                     PC3-10700 (667MHz)

both are 1.5v rams

[DGroves]

t HP ships the system with  DDR3 Non ECC  1600 also known as PC3-12800

AMD based systems (and some intel) can have a bottom limit on ram speed meaning if slower than listed ram is used the system memory controller can not step down that slow and the system will refuse to boot

your system appears to be unable to use slower ram assuming you have installed the ram in the correct order 

A memory module can be installed in only one way. Match the notch on the module with the tab
on the memory socket.
Populate the black DIMM sockets before the white DIMM sockets

http://h10032.www1.hp.com/ctg/Manual/c04497146

https://support.hp.com/us-en/product/hp-elitedesk-705-g1-small-form-factor-pc/6893874/document/c0442...