I have had Fallout 3 for a long time, and only just recently installed the DLC pack from the GOTY edition and found that after installing, the game crashes at start up every time unless I un-install everything and re-install only the base game without the DLC.

Has anyone experienced this? or can anyone help!? Many thanks!

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System Information
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Operating System: Windows 7 Ultimate 32-bit (6.1, Build 7600) (7600.win7_rtm.090713-1255)
Processor: Intel® Core™2 Quad CPU Q6600 @ 2.40GHz (4 CPUs), ~2.4GHz
Memory: 4096MB RAM
Available OS Memory: 3584MB RAM
DirectX Version: DirectX 11
DX Setup Parameters: Not found

Card name: ATI Radeon HD 5600 Series

Tried the Multi-Core Fix?:

Find your .ini file in your My Documents\My Games\Fallout3 folder ...it is the configuration settings file named FALLOUT

Open it with notepad and do a CTRL+F to search for the line

bUseThreadedAI=0

.....change it to =1


and below that line add this line

iNumHWThreads=2

If it is crashing before getting to the main menu it could be missing or out of place master.
Give us a few more specifics and post your load order.
Please use the spoiler syntax when you post your load order, like this without the question marks - [spoiler?]your text[/spoiler?]