Doesn't sound like a very useful test if that's the case.
Well you start by testing the system and removing parts and looking at the results. It is a pretty typical test. If the netbook doesn't have enough CPU to generate 1gb/s of network flow, then right off the bat you can tell the netbook would be the bottleneck since even if it had a RAID0 of 12 SSD drives, you would never max out the NIC because the CPU simply can't handle the load so the file transfer would never max out the network.
Typically with iperf you would get a pair of laptops, do the test via a single cable, laptop to laptop and use that as a baseline (most centrino and better machines should be able to load up a 1gb/s network without issue.) Then plug them in over the segment you want to test and look at the results. It the flow is still 1gbps, then "the network is slow" isn't the network and you start checking disks and the like. If the speed drops to 100mb/s (and there isn't supposed to be a 100meg connection anywhere etc) you know that something is broke and you keep moving up the chain.