It used to work normally and I was able to create new neighbourhoods till few days ago, now when I try to create a new neighbourhood it doesn't stop loading and it just continues to switch from 'creating pets' to 'creating magic' and 'creating pets' again and then back to magic and doesn't stop.
I have all expansion packs except Mansion and garden stuff. I have appropriate patch for the game.
I tried removing downloaded stuff and 'groups.cache' and 'accessory.cache' and also resetting the neighbourhoods. None of it worked so I wanted to try to reinstall the game but I'm not able to do that either, can't uninstall any of the expansion packs nor the game... I'm not sure what to try anymore

How many neighborhoods do you have? Each neighborhood that you add puts additional strain on your computer; perhaps you've reached your limit.

What happens if you backup your save game and remove all of your existing neighborhoods? Are you then able to create a new neighborhood?

Have you got enough hard drive space? Each neighborhood takes up additional space; if you don't have enough space the game could have problems.

I have neighbourhoods that came with the game and 5 that I created (and in some are extra university, downtown, vacation...neighbourhoods). I tried to backup neighbourhoods and to remove them but it didn't work and I have enough space on hard drive but thanks for advice!

Do you mean you couldn't remove the neighborhoods, or that it didn't help?

that it didn't help

It's possible that your stealth subhood templates have become corrupted.

To test this theory, disable all of your stealth neighborhoods by renaming NeighborhoodTemplate to NeighborhoodTemplate_Stealth for all of the EPs which have been installed. Here are the standard locations of the stealth neighborhoods. If your games are not installed in the standard locations, look for the names of the individual stealth hoods:
C:\Program Files\EA GAMES\The Sims 2 Pets\TSData\Res\NeighborhoodTemplate\P001
C:\Program Files\EA GAMES\The Sims 2 Seasons\TSData\Res\NeighborhoodTemplate\G002
C:\Program Files\EA GAMES\The Sims 2 Bon Voyage\TSData\Res\NeighborhoodTemplate\V001
C:\Program Files\EA GAMES\The Sims 2 FreeTime\TSData\Res\NeighborhoodTemplate\F002
C:\Program Files\EA GAMES\The Sims 2 Apartment Life\TSData\Res\NeighborhoodTemplate\E002

Depending upon your operating system, you may have to turn off UAC (user account control) to be allowed to make those changes.

If disabling those templates allows you to create a new neighborhood, then one or more of the templates may have been corrupted. Start renaming the folders back, one by one, until you experience the problem again. That will tell us which template is corrupt.

If that doesn't help, then perhaps your Pleasantview template has become corrupted. You can disable the base game neighborhoods by renaming
C:\Program Files\EA GAMES\The Sims 2\TSData\Res\UserData\Neighborhoods
to Neighborhoods_Original

Again, let us know whether this solves your problem.

You can rename all of the folders back to their original names once you've done these tests.

One more thing: this could also be a hardware problem. Could you give us your system specs, please?
http://simswiki.info/wiki.php?title...lp:System_Specs