Looking for a client with a particular function

I've been trying to find a client that can download a file at any arbitrary location.

I'm stuck on dialup and many times I've downloaded an iso or divx only to find there's a corrupted chunk in the middle or end from a bad resume (perhaps after a computer crash). And instead of having to spend another 4 days downloading it all over again, it would be very useful to tell the client to download from only the xxx'th byte to the xxx'th+1024 byte so I could then patch the data right into my corrupted copy. I've done this several times before when the corruption is towards the beginning of the file and doesn't require much re-downloading.

Does anyone know if such a thing exists? I know I could even just use an http client If i could find a way to get the FILE-ID returned from the gnutella clients without having to write my own from scratch.

Thanks, kungfo0.