How can I Remove Custom Pois from Garmin Nuvi?

Probably the easiest way to remove "Custom POIs" from the device (a 765 like the the one I use) is POI Loader. Even though you are asking for another way, let me detail the steps.
1. Open POI Loader
2. On the Welcome screen, click Next
3. on the "Select" screen, choose "Garmin Device" and click Next
4. On the "Select Device" screen, let it find the 765 and click Next
5. On the next screen, push the button the says "Remove all previously installed custom POIs from your device" and click Next

Having detailed what I think is the safest way, here is how to delete "Custom POIs" using the computer.

Attach the computer and let the device be found. Likely, you will get a dialog box that will let you "View files and folders".

Navigate to the "Garmin nuvi(x)/Garmin/POI" folder and delete any ".gpi" files that you find there.

I am not aware of any device that has the option of deleting "Custom POIs" from the device itself.

Welcome to the site.

We usually recommend the following.

There is a "Learn" button in the upper right of this page next to "red light cameras" that takes you to a Getting Started page. It is worthwhile visiting this page.

To make navigation easy, most browsers provide the following option. When you want to follow a link - but still keep your current page open - you can hold down the "Ctrl" key as you left-click on a link. That action will open a new "Tab" in your browser up on the "Tab" bar. When you then left-click on that new "Tab", you will follow the link - leaving the "Tab" you are now reading open and available to click on and return here.

So, using the "Learn" link, you might try the "Ctrl" - left-click sequence and then return here. You can return by either "X-ing" out of the "Getting Started" page (using the "X" on the "Tab" itself) or just left-clicking on the "Tab" for the page you are on right now.

Note that the Learn Button will give you access to two valuable reference pages -
the "Index" to all of the FAQs (Frequently Asked Questions) and the Glossary of Terms and Links.

Since you are new here, I encourage you to go through a couple of the Tutorials.

The first link makes sure the settings on your computer are such that you can do more advanced POI loading.
http://www.poi-factory.com/node/30393

The next link helps you make a backup of your GPS by attaching it to your computer. (NEVER do anything to your GPS until you have a backup). It also assures that you put your (newer) unit into a state where you can see all of the folders there.
http://www.poi-factory.com/node/30394

Let us know how we can help you enjoy your GPS.

Delete the .gpi files in the folder under the Garmin folder named .poi. (I'm doing this from memory. The folder name may be something different, but the file extensions are all '.gpi'.)

Late to the dance again...

As Camerabob said its the .gpi file. If you cannot find a file with the .gpi extension, but see a .gpx file do not delete that file as its your favorites file. I'm hoping that that's whats those extensions were way back when (2008)..lol

AFAIK the folder name is POI.

As an aside it doesn't matter if you delete current.gpx as your device will recreate it when it boots.

Correct

Just be aware that your nuvi will also hoover up .gpi files whether they're in the POI folder or not, so if you can't find them there look elsewhere.

The explanations are very clearer. Thanks.
One last question:
Nowadays, is there some Garmin model that allows deleting custom pois FROM THE DEVICE ITSELF, as with waypoints?
Thanks a lot.

Afraid not