Well, I found a download that fixes a lot of errors in the game. The end result is that the game crashes much less frequently. It's pretty much a requirement for PC players. You can download it here:
Error Corrections - Reduce CTD at Fallout 3 Nexus - Fallout 3 mods and community
Also, running the game as administrator seems to help with crashes. (right-click on launcher, and select "run as administrator")
Also, if you have your fallout game files installed in your program files folder: Windows 7 has problems with this sometimes, so you may want to move the files to just outside of the program files folder.
Also, I found a mod that will prevent Windows Live from running in the game (WL can sometimes prevent Fallout files from loading, causing the game to freeze/crash. You can download it here, make sure to read the notes though, and I believe that it will also disable achievements:
Games for Windows LIVE Disabler at Fallout 3 Nexus - Fallout 3 mods and community
Also, if the launcher won't work, you can skip the launcher and just double-click on the Fallout3 application itself, this will usualy bypass the launcher and start the game automatically.
Lastly, the i3/5/7 cores have two cores. Fallout 3 wasn't made to work with multi-core CPUs, and this creates problems when it is run with W7. You will have to edit the ini file to make it work. Here's what you need to do:
Open the FALLOUT.ini file located in My Documents>My Games>Fallout 3 and find the line:
bUseThreadedAI=0
change the 0 to a 1
then below it add the line
iNumHWThreads=2
This will properly configure the game to run on your computer.
I hope this helps you.