Most of the solutions I found were memory based. For example, load into a dictionary(associative array, hash, map etc.) and write it back out. Same problem. I couldn't find a free Virtual Memory backed dictionary. Scripting.Dictionary would do it for small data, but I suspect if would crap out processing a GB file.
Others were use a db. Linux solution is likely the simplest. Plus it's derived from a system that's done that type of stuff for a long time. Not Windows.
There should be some free Windows editors that handle files of arbitrary length. Try Softpedia. Just so you can look through the file without loading the entire file in ram. When you change file position you have to wait for some disk churning is all.