I have enjoyed playing Fallout 3 for a while now and have got to the point where i need to go to vault 112 to continue the finding dad quest but as i leave Megaton to go there i keep getting a RTD Crash as i go over a ridge....
I have installed all the patches and reinstalled the game 3 times but it still crashes at the same spot. Can anyone help me ?

PC SPECS

Intel Pentium 3 2.6 ghz
2GB Ram
512mb Nvidia Geforce 7600Gs
400gb HDD ( 117 Gb Free)
1600 x 900 21.5 inch Monitor ( I play the game at 800 x 600 )
Direct X 11 installed