Any errors your file system has may snowball over time until there are
serious errors and/or corruption occurs, so, for example the OS won't load,
or some program may crash consistently because one of it's DLL's is damaged.
You can run chkdsk from a command prompt and it will notify you if you have
any errors that need fixing. Typing chkdsk will run in read-only mode, so it
won't do any harm.
Running chkdsk after a crash isn't a bad idea, as some file/file system
corruption may occur as a result of the crash.