From what I recall, Origin had a digital download for ProStreet, but later dropped it. It's possible that ProStreet was dropped because the licensing server was shutdown, but I'm not sure. The securom licensing server used for later NFS games was shut down somewhat recently (within the last year), and there are some threads in this forum about that. EA has a workaround for some of the affected games, but not all of the affected games.
In my opinion, I think you'd be better off getting a DVD drive for ProStreet, and other older games , since the CD/DVD versions of games don't rely on licensing servers that may get shutdown in the future (or are already shutdown). The last NFS games on DVD that I'm aware of are NFS Undercover and Shift 2 Unleashed, which only need the DVD during install, but not to play. Prior NFS games like Shift 1 do require the DVD to play as well as to install.
