The Western Digital Black SN850X hard drive with Heatsink (2000GB, M.2 2280) is generally compatible with Acer Predator Orion 3000 computers, including the PO3-640 model, but there are a few considerations:

## Compatibility
- The WD Black SN850X is a PCIe 4 x4 NVMe drive, which means it is compatible with the M.2 slots on the PO3-640 motherboard.

## Internal space
- Although the hard drive itself is compatible, the heatsink could cause space problems. Heatsinks on SSDs can be too large for some M.2 slots, especialmente if they are close to other components such as graphics cards or sound cards.
- However, for the PO3-640, it was mentioned that the M.2 slot is often in an open space and benefits from the airflow from the front fan, which makes the heatsink less necessary. You might therefore consider buying the version without heatsink, but if the price is the same, the version with heatsink should still work if you check the dimensions and make sure there are no conflicts with other components.

To sum up, the hard drive is compatible in terms of technical specifications, but make sure you check the dimensions and the location of the M.2 slot to avoid any space problems.