"Can Linux access the local windows disks? "

Any sensible recent Linux can access FAT, FAT32, and NTFS, for both read and write.

Ideally you'd find a reliable pair of test programs that don't involve the disk, if what you want to measure is NIC/network performance.

Perhaps a Linux expert could suggest a LiveCD to choose, and/or suggest whether simple test programs (not necessarily ftp, samba, etc) are readily available.

But if Windows is your chosen environment, testing under Linux may be a distraction, as it probably won't help improve Windows performance (unless the Linux tests help discover and fix a problem with the NICs or the network).

Best of luck anyway.

After some further investigation I believe the issue to be with the old Dell PC - when copying files from it or to it, the CPU usage maxes out at 100% so it looks like it can't cope with the overhead. NIC usage peaks at 26% but is 17% average. On the other hand, the newer PC CPU usage maxes out at 25%.

So I've given up speed testing for now, at least until I get another newer gigabit NIC-equipped PC.

The good news (I think) is that copying from one PC to the other takes the same time across my home LAN as it does with the PCs directly connected without a switch or anything else on the network, so hopefully when I do test speeds with another faster and more modern PC, I'll be getting the sort of speeds reported by others in this thread, in the order of 700-900 Mbps.

Thanks for all your help and advice, I've learned quite a bit from your feedback.