My younger brother has played Minecraft on his laptop (Windows 7 PC) before, but recently the launcher has been crashing on him and giving him this error below. I have tried both re-installing the game completely and disabling the firewall on our anti-virus program with no luck still.

[18:31:03 FATAL]: Fatal error launching game. Report this to http://bugs.mojang.com please!
java.io.FileNotFoundException: File 'C:\Users\Noah\AppData\Roaming\.minecraft\assets\indexes\legacy.json' does not exist
at org.apache.commons.io.FileUtils.openInputStream(FileUtils.java:299) ~[launcher.jar:1.6.43]
at org.apache.commons.io.FileUtils.readFileToString(FileUtils.java:1711) ~[launcher.jar:1.6.43]
at net.minecraft.launcher.Launcher.cleanupOrphanedAssets(Launcher.java:254) ~[launcher.jar:1.6.43]
at net.minecraft.launcher.Launcher.performCleanups(Launcher.java:496) ~[launcher.jar:1.6.43]
at net.minecraft.launcher.game.MinecraftGameRunner.launchGame(MinecraftGameRunner.java:231) ~[launcher.jar:1.6.43]
at com.mojang.launcher.game.runner.AbstractGameRunner.onDownloadJobFinished(AbstractGameRunner.java:186) [launcher.jar:1.6.43]
at com.mojang.launcher.updater.download.DownloadJob.popAndDownload(DownloadJob.java:122) [launcher.jar:1.6.43]
at com.mojang.launcher.updater.download.DownloadJob.access$000(DownloadJob.java:12) [launcher.jar:1.6.43]
at com.mojang.launcher.updater.download.DownloadJob$1.run(DownloadJob.java:86) [launcher.jar:1.6.43]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [?:1.8.0_25]