Corrupt archives on home networks?

I recently installed XP on both my rigs. I'm trying to get my backup house in order. My primary rig's dvd burner can't be trusted any more, so I set my home network up again. It seems to be working fine, but like when I had them networked with W2K, archives always transfer corrupted (large RAR archives always gave a "header not found" error but extracted okay).

I backed up a 40 gig runtime with Acronis. All files validate fine on that rig. Last night I transferred them (using Copy Handler 1.28) to my 2nd rig and Acronis won't validate; instantly returns "not valid."

I built the archives as ISOs before transferring them, and to make sure I moved them off the virtual drive and Acronis still instantly spat them out. Just to make sure I mounted the image on a virtual drive on the 1st rig and sure enough, Acronis wouldn't eat that either.

So, I'm retransferring now, sans the ISO part. I'll retest when that's done. But in the meantime I'd like to know what the old hands here have to say, and if there are any apps designed to make rock-solid error-proof transfers across home networks. I've never been into the FTP thing - is that what I need, a good FTP app?

Update: yep, I retransferred the first archive and Acronis spit it out again on the second rig. I just checked it five minutes ago on the first rig and it was fine. And Copy Handler reported no errors in the transfer.