If you look at the rear of that Compaq CQ2000 series case, you should see a 3-prong port in its power supply unit that looks like this:

This is what a 3-prong power cord looks like that you plug into it:

It can be a different color or different length, but that doesn't matter.
Desktop 3-prong power cords are pretty much interchangeable.
You don't need to buy one that's a certain length or specific part number.

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If you look at the rear of that Compaq CQ2000 series case, you should see a 3-prong port in its power supply unit that looks like this:

View attachment 259486

This is what a 3-prong power cord looks like that you plug into it:

View attachment 259487

It can be a different color or different length, but that doesn't matter.
Desktop 3-prong power cords are pretty much interchangeable.
You don't need to buy one that's a certain length or specific part number.

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Many thanks. I thought the cord was like the ones used fo laptops. That's what shows up on searches.

 

I resurrect and update older desktops, so I have several 3-prong power cords in my parts box.
I don't recall ever having a problem with using a certain length/color power cord with a certain brand/model desktop.

On a side note.
Some of the newer lost-cost brand/model desktops no longer have an internal power supply unit, so they use a power adapter similar to what a laptop uses.
If your Compaq CQ2000 is one of those, that's a different story.

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Well the CQ2000 DOES use a laptop PSU, however it's just a generic HP 65W power adapter with center pin connector so it's fairly common. 90W and 130W blocks will work too but 65W will suffice, it's lighter and smaller too.

Look for an HP 65W power adapter with this connector:

 

Jacky:
I didn't know if his Compaq CQ2000 series desktop has an actual power supply unit or uses a laptop-type power adapter, so that's why I mentioned both options.
I'll leave OptimistDK with you.
Frank

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Many thanks for your expert help, the 90 watt cord did the trick.
Best,
Arthur (OptimistDK)