Make sure you back up your game before you begin. After that, simply go into your documents where your Sims 2 folder is. (Not The x86 Folder!)
1. Make a new folder called whatever you want to call this game. I called my current Sims 2 Game.
2. I made another new folder called Downloadscurrentgame
3. I placed all of my downloads in that new folder and turned them into a rar file. I then placed them in my 3T external HDD. It left the downloads in folder format to be zipped again though.
4. Place the new game folder into your documents folder.
5. move your entire sims 2 folder into this new folder. It may tell you that you have to be an admin to do this, just click yes and keep going.
6. Zip it up with winrar. This can take a while if you have a lot to move.
7. Save it to a big flash drive or an external HDD.
8. Move it to the new computer.
9. Once on the new computer. Run the sims 2 once without adding your current game
. While in game click enable custom Content
10. Come out of game.
11. Clean everything out of that sims 2 folder the game just created
12. Unzip your game into the new folder. Until all is unzipped and in place, downloads included. Make sure you rename your Downloads folder Downloads because we changed the name, remember?
13. Ok, now with it all unzipped, go back into game.
14. It should run perfectly! It will take a few plays for all of your mods to show up and some content, but there will be no blue flashes.
15. You can do this if you were playing on a guest account on your computer too. You need to use the same steps.
I hope this was helpful.