Minecraft Forums

I keep trying to play minecraft and it will not work. This is the error that keeps happening:

Looking for update
Downloading: https://s3.amazonaws.com/Minecraft.Download/launcher/launcher.pack.lzma
Got reply in: 619ms
No update found.
Reversing LZMA on C:\Users\David\AppData\Roaming\.minecraft\launcher.pack.lzma to C:\Users\David\AppData\Roaming\.minecraft\launcher.pack
FATAL ERROR: net.minecraft.bootstrap.FatalBootstrapError: Unable to un-lzma: java.io.FileNotFoundException: C:\Users\David\AppData\Roaming\.minecraft\launcher.pack (The file or directory is corrupted and unreadable)
at net.minecraft.bootstrap.Bootstrap.unpack(Bootstrap.java:146)
at net.minecraft.bootstrap.Bootstrap.execute(Bootstrap.java:123)
at net.minecraft.bootstrap.Bootstrap.main(Bootstrap.java:381)

Please fix the error and restart.

How do I fix this without losing all my data?