had same error so I moved the Fixt folder into 'Fallout 1 English' subfolder and it starts from there

It's been a while, but I'll see if I can find the link so you can see what all it contains and the site has all the instructions if you decide later.

But here are a few things it adds:
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- One of my biggest. It allows you to push NPCs out of the way like in FO2. I've had to reload an older save a few times cause NPCs wouldn't move and blocked my path.
- FO2 trading window. Larger amounts of caps can be traded per FO2.
- More advanced combat options for your companions per FO2.
- More fixes included than the outdated Fixt (this is based on user comments, so I can't verify and I also don't know when Fixt was last updated; but according to the 2yr old post, it was 5 yrs, so that means 7 yrs outdated now)

Also, I have an inventory filter when I checked last night, but I don't know if it was part of FO Et Tu or FOTweaks (and I think FO Et Tu already includes FOTweaks, but will have to look at the notes again). This filter quickly allows you to sort armor, ammo, med items, misc items, all into their own tab. This applies to the trade window too, for both you and the NPC you are trading with. So most times you no longer have to scroll thru that huge single list lol.

I could include some screenshots if you like so you can get an idea what the FO Et Tu looks like. I'll also try to get the official link to it.

This is in no way my advocating you use this. I just feel it's more convinient with lots of QoL improvements and it's another option for those interested. Always play the version that you want for the best experience. You can't go wrong that way lol.
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Edit:
One big thing I sorta assumed and now I probably shouldn't have lol. FO1in2 required both FO1 and FO2 to be installed, since FO1in2 imports the FO1 master dat file to FO2 game and that seems to be how the FO2 engine seems to run the FO1 game. So owning FO2 is required, so I guess I dropped the ball on that when I first replied, sorry about that.
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It didn't help, unfortunately. Does someone know what might be the cause of that CD search?