But when I tried to put a patch (not on pets, on the base game) It crashed my game and it was Awful.... Are you sure I should do that?
It's been a very long time since I patched base game, so I won't hazard a guess why that patch crashed your game, but that patch had a lot of important fixes in it. Unpatched base game has a few very nasty problems - main thing to know is that all the base game lots in your lotbin are unsafe. You need to go into each one in build mode and edit something before you move any sims in. Search MATY ro google for "the bomb that killed happy valley". Here's one...
http://www.moreawesomethanyou.com/smf/index.php/topic,303.msg8952.html#msg8952The Pets patch obviously won't work on base game, but if you've just added Pets, yes you should add the Pets patch.
To protect your game, make a back up of your game before you install anything like a patch or EP. Simplest is to back up the whole Sims2 folder, but you can just do key bits like 'hoods and downloads if you want. That way, if anything goes wrong, you can get back to where you were. If you are really worried, take your entire Sims2 folder out of My Documents, start up the game and check that everything is OK in one of the newly generated template 'hoods. Re-enable CC in the game options, then quit. Next, put your own stuff back. Don't overwrite the folders - delete and replace or you'll mix up two versions of Pleasant view and have a real mess on your hands.
I'm not good at step by step instructions. Check out the how to's on MTS2 ...
patches
http://sumomo.modthesims2.com/wiki.php?title=Game_Help:Patching_Your_Gamebacking up
http://sumomo.modthesims2.com/wiki.php?title=Game_Help:Back_Ups