Boot a tiny Linux environment -from USB

I have a USB dongle with GRUB4DOS, it's NTFS with a Windows 7's boot loader. I would like to add a boot entry, prior to loading Windows 7, of a tiny Linux environment - which is capable of executing '7z' for extracting a file, exit - and continue to Windows 7's boot loader. The Linux environment should load *very* fast. No need for lan. No need for wifi. No need for bluetooth. No need for gui.