DSL seria sua melhor aposta, mas você pode experimentar uma instalação mínima de Arch . Já que com o arco você constrói o sistema a partir da base.
Arch provides a minimal environment upon installation, (no GUI), compiled for i686/x86-64 architectures. Arch is lightweight, flexible, simple and aims to be very UNIX-like. Its design philosophy and implementation make it easy to extend and mold into whatever kind of system you're building- from a minimalist console machine to the most grandiose and feature rich desktop environments available. Rather than tearing out unneeded and unwanted packages, Arch offers the power user the ability to build up from a minimal foundation without any defaults chosen for them. It is the user who decides what Arch Linux will be
- Arch Linux Wiki
Tenho arch instalado em 500MB de RAM, 2GB de armazenamento e CPU Intel de 500 MHz. Um apertado no armazenamento , mas de outra forma perfeito.
EDIT: Note que o arco só funciona em sistemas de base i686 e x86-64
Caso contrário, ouvi coisas boas sobre SLAX