error during startup see log for details

jessw89  Since your packs are all installed, you may be able to find the codes in your computer's registry.  Here's how to look:

https://sims3.crinrict.com/en/2013/09/how-to-find-your-serial-number.html

If you can find the codes, try registering them in the EA App, or better yet, on the old Sims 3 site if your account there works, which it should.  Even if you'd rather use a disc install, it's great to have the content attached to your account.

For the error itself, you'll need to do a clean uninstall and reinstall of Sims 3, as described here:

[Read First] Running Sims 3 in Windows | EA Forums - 8323446

The question is whether you want to use the EA App to run your game, or you want (or need) to reinstall via disc.  There are advantages to both, so pick the one that works for you, if you can in fact register your content.  And external CD drives are cheap if it comes to that.

puzzlezaddict 
Thanks, Ive had a quick look but I'm going to need to come back to this later tonight and make lists and see what will register or not.

There seems to be three sets of this data within the registry files and that just doesn't seem right? 

There is one copy here formatted with pack names
Computer\HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Electronic Arts\Sims\The Sims 3 Into The Future

Another copy here partially listed like this and partially just \*bunch of numbers*
Computer\HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Origin Games\sims3_ep03_dd

And then another set here with some of them listed here but most of them listed under two folder deeper under Sims\The Sims3\DLC
Computer\HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Sims

Some instances have codes, others do not. Some have them in one version but not another, some the other way round. 

There is definitely only one instance of the installation files and documents files though, so are some of these just left over files from the switch from disk to forced origin use to forced ea app use? 

(Makes me want to clean install windows looking at that mess 🤣🤣)

jessw89  It's definitely true that disc and digital installs have different types of registry entries.  But I'd expect every pack you installed via disc to have the same type of entry, with the ones in your EA App library perhaps having a second one.

What I can say for sure is that having mismatched entries like this is the most common cause of the "error during startup," so yes, you'll need to wipe away everything (but not Windows) before reinstalling.  But hopefully you find codes for your missing packs somewhere in that mess.  Every entry should have a number of individual values associated with it, one of which should be the product code.  However, it's very possible with Origin or EA App installs, that particular string is missing or just a bunch of zeroes since that's not how ownership is validated in a digital install.

Point is, for any pack the EA App thinks you don't own, check every value for every associated registry entry to make sure you're not missing something.  The sims3_ep03_dd entry at least should be Late Night, Digital Download (Origin installed or verified), but Origin may not have recorded your product key in this particular entry even if LN was registered to your account.