The absolute latest version that supports Windows 7 32-bit as a host is . While version 6.0 and above offer newer features, they officially removed support for 32-bit hosts.
Since Windows 7 is no longer supported by Microsoft, using an older version of VirtualBox adds another layer of legacy software to your stack. Ensure you download the "Extension Pack" that matches your specific version number to get full USB support. virtualbox for windows 7 32 bit
Let's assume you want to run (a classic pairing) or Ubuntu 16.04 32-bit . The absolute latest version that supports Windows 7