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 Windows 7. 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:
change the 0 to a 1
then below it add the line
This will properly configure the game to run on your computer.
I hope this helps you.