Driver Backup! 2 is a free, portable DriverMax alternative
Driver Backup! 2 is a nice alternative. While it doesn't have DriverMax's extra features (like driver updating), the just-under-1mb application provides fast, simple driver file backups and restorations.
Two other features I enjoy are that it's fully portable and supports command line switches for fully automatic operations. Even better, there's an integrated builder that will help you create your command line easily - as long as you can read a little Italian.
English help files are provided, though, and fully document the available switches. Setting one up manually is easy enough that you don't really need the builder's help anyway.
Both backups and restores are quick and painless, and it had no trouble with my Windows Vista x64 install. It's well worth adding to your USB flash drive.