basically I want to make sure my personal folder (emails, documents, contracts, IP) is not being exposed by random software I download.
Se estamos falando de "software aleatório", então Sandboxie pode ser sua coisa.
Sandboxie runs your programs in an isolated space which prevents them from making permanent changes to other programs and data in your computer.
Não faz exatamente o que você quer imediatamente. Do FAQ:
It should be noted, however, that Sandboxie does not typically stop sandboxed programs from reading your sensitive data. However, by careful configuration of the ClosedFilePath and ClosedKeyPath settings, you can achieve this goal as well.