From their web site:- HP Certified Refurbished Products are products that have been returned to HP and subsequently undergone a refurbishment process prior to being re-offered for sale. HP Certified Refurbished Products undergo a rigorous quality refurbishment process designed to ensure that they perform to HP’s high standards
e.g.
HP 110-501a Desktop (Refurbished) $239 inc GST.
46% Off, Save $190
RRP $449
Refurbished Product
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Intel® Celeron® J1800 Processor (2.41 GHz, 1 MB cache, 2 cores)
Windows 8.1 64
Intel® HD Graphics
4 GB 1600 MHz DDR3L (1 x 4 GB)
1 TB 7200 rpm SATA
1 year warranty is nice for a used PC, but you can do a lot better and/or cheaper getting an ex-lease Dell from eBay.
I know they are not proper manufacturer refurbs like the above, but they are still reliable. Especially if you replace the old HDD with a new SSD.