You can hide any file inside of another file just by typing:
type sol.exe > container.txt:sol.exe
and to run the file hidden file just use:
start c:\hide\container.txt:sol.exe
But the crazy part about this is it doesn't increase the size of the file (so it's totally hidden).
And if you delete the file with the hidden stuff inside, the hidden stuff doesn't get deleted. Just use:
more < container.txt:sol.exe > sol.exe
Why does NTFS allow this? It seems like the best way to hide a virus.