Same error for me. I have WinXP too; it work with Oblivion, Skyrym, Fallout NV.. but not fallout3, its seems like its cant create a new masterlist.txt LOOT doesnt work neither Pd loot does not work on XP I solved the problem but still has the Error: 4294967295. I just download the masterlist.txt from Boos masterlist URL location found in settings or boos.ini, then paste in the right location (Boss/Fallout , in my case) Then i moved (or delete) the directory where saves and .inis are (my documents/mygames/fallout) Then run the Launcher to detect my hardware and run the game, its create new save files and .ini . i copy the old saves to the new directory. Boss work and sort my mods but stil show me the Error masterlist update failed. but is not a real problem.