Hi Ian Serrano
The hard drive has nothing to do with POST so we can ignore that for now.
For POST you need main board, processor, PSU, and ram.
"new" doesn't always mean it is good.
Try swapping ram. Use only 1 ram stick and then try the other.
When you say the parts are new, when were they new? Are they new due to trying to resolve the problem?
Make sure the processor is attached properly and no bent pins and heat sink (with thermopaste) attached.Trouble shooting tips