What is the best way to transfer about 15GB of videos from one networked PC to another?

My one desktop has XP and 1.1 USB ports so the USB HD i tried with it said it would take about 1.5 days to transfer.
then I tried a DVD but the file is too large...

I'm currently running though the network but my sister is complaining of it slowing that computer down a lot and now she is saying she will cancel the transfer but I don't want that because I know it runs a risk of messing up/loosing some of the files.......
i would say just use the USB HD's, it probably won't take anywhere near that long to complete the transaction, maybe 6 hours at the most.
I have a few files...each about 4-5GB

The 1.1USB is by far the slowest...I'm upgrading them soon with a new card just for that reason...I'll also put a card with a few firewire ports on it in there.

The network seems to be the fastest way from what I'm seeing right now.

thanks for the info everyone
well you could use the dvds....derr just dont put all of them on the same dvd use a few, and than you'll have some back up to, maybe use an ipod