I downloaded Marka's Beginning of Riverblossom Hills, extracted it to my Desktop, then followed the installation instructions to put it here:

Windows Vista/7/8: C:\Program Files(x86)\EA GAMES\The Sims 2 (Your Latest EP)\TSData\Res\Catalog\Bins

I started up my game, and there was no Riverblossom Hills. So I tried the other installation instructions, and put it here:

Windows Vista/7/8: Users\(Current User Account)\Documents\EA Games\The Sims 2\Downloads\

Then I started up my game again, and again Riverblossom Hills did not appear. Surely the installation instructions should have made some reference to Neighborhoods? Can You tell me where I should put that file?

[Edit] Still trying. Next I put it in Program files\The sims 2\TSData\Res\UserData\Neighborhoods. That didn't work, either. Any ideas?

You should put the entire folder into C:\Users\(your computer name)\Documents\EA Games\The Sims 2\Neighborhoods. Instructions are in the download thread.

Did you tried to place the neighborhood in: C:\Users\(your computer name)\Documents\EA Games\The Sims 2\Neighborhoods
I always place custom sims 2 neighborhoods in the "Neighborhoods" folder. And all the custom neighborhoods loads fine in my game.
Just let me/us know that the custom neighborhood appear for you if you put that hood in that folder.

EDIT: Klaartje posted the answer sooner than me while i was answer the phone while typing this post

Yes, I did that too. It doesn't show up. What am I doing wrong?

No, they are not. The instructions I quoted in my first post were copied and pasted from the download thread. You see the word 'neighborhood' did not appear in the download thread.

EDIT: i have edit this post because i have installed the hood wrong. My mistake

You said you put it into Program Files\Neighborhoods. It needs to go into Documents\Neighborhoods. If that still doesn't work, please post a screenshot of your neighborhoods folder and a screenshot of the N341 folder where you installed it.

I got it! I forgot to place "RoseGreenman" package in the Savedsims folder. And that was why that hood didn't show up in my game.

Try this: Download that neighborhood and open the "thebeginningofriverblossem" folder. Put the "N341" folder in (C:\Users\(your computer name)\Documents\EA Games\The Sims 2\Neighborhoods) and place "RoseGreenman" Package file in (C:\Users\(your computer name)\Documents\EA Games\The Sims 2\SavedSims) folder, and the hood will appear in the game. That hood looks lovely in the game.

And thank you Klaartje for your help.

I have done both of those things - in fact I have re-started the game eight or nine times today, in an effort to get the new neighborhood to show up. Sorry, I can't post a screen shot - I don't know how to. I brought up my neighborhoods folder, with the Desiderata folder duly showing (it was Desiderata, not Riverblossom Hills) and pressed the button bearing the legend 'PrtScn', but what to do with that I don't know. Desiderata is, apparently, in my Neighborhoods folder, but not in my game.
By the way, the file I have is called 'Desiderata', not 'N341'. In Properties it has 10.5 MB, so it is the right size for a neighborhood. Do you think I have the wrong file?
#amazingsims:Try this: Download that neighborhood and open the "thebeginningofriverblossem" folder. Put the "N341" folder in (C:\Users\(your computer name)\Documents\EA Games\The Sims 2\Neighborhoods) and place "RoseGreenman" Package file in (C:\Users\(your computer name)\Documents\EA Games\The Sims 2\SavedSims) folder, and the hood will appear in the game.
I've muddled things up by misremembering the name of the neighborhood. It was 'The Beginning of Desiderata' N340, not 'The beginning of Riverblossom' N341. Can you adapt your advice so it will make sense to a very dull simmer?

You will get a folder called "TheBeginningofRiverblossom" inside of this folder after you extract it with rar or 7zip.
Inside is a folder called N341 this folder needs to be copied to your "C:\Users\(your computer name)\Documents\EA Games\The Sims 2\Neighborhoods"

And for Rose Greenman.

Place RoseGreenman.package in your C:\Users\(your computer name)\Documents\EA Games\The Sims 2\SavedSims

If the above does not work you may need to delete the "NeighborhoodManager.package" inside of the Neighborhoods folder.
"C:\Users\(your computer name)\Documents\EA Games\The Sims 2\Neighborhoods"

If it still does not work then I am all out of idea's on your problem.

Yes! I looked into the file called Desiderata, and it contained N340 and a picture and a script. So I just pulled out N340 and dropped it into Neighborhoods. And it works! Thank you for all your help.