Ooh, true we cannot handle files larger than ~2GB as a soft maximum; serious problems increasingly crop up as we've tried to pass that boundary. You might consider splitting your file into two or more separate files, each assigned to a separate product, then use our "Package files from other products" setting to create a "bundle" product that issues download links for all those files at once:
Also bear in mind how long you'd be expecting buyers to babysit a download that large. Any download can only be as fast as the slowest link in the chain, which is usually the buyer's own ISP connection. Over a typical residential broadband connection of 1.5Mbps, it would take at least 3 hours to download a 2GB file, or about a full day over a basic 256kbps DSL connection, never mind the several days it would take over dialup connection.
For sellers with extremely large files such as yours, we've been recommending our SwiftCD integration to have them automatically duplicate your files/data to a CD/DVD and mail that to buyers on-demand whenever an order comes in:
However, we've just found out that SwiftCD has recently started requiring a minimum contract dealing only with incorporated/LLC businesses, so if you're not an incorporated company or not willing to commit to a contract, you may need to find another CD/DVD fulfillment service that can accept PayPal IPN, which is the format our generic Integration feature follows. As long as they can accept IPNs that don't come from PayPal, don't need to validate IPNs with PayPal (which would fail since we are not PayPal, and we validate the original IPN with PayPal anyway before we forward it), and can handle or ignore the extra fields we add to the basic IPN data set, they should be able to work with our Integration feature to send discs automatically for you.