Transferring data
I never bother with transferring data via a serial connection, it's really slow. I almost always take 1 HD out of one PC and plug it into the other temporarily in place of a CD/DVD drive. Then on boot, the bios will detect the second HD, and so will windows, giving it a higher drive letter. Then you just drag-and-drop, use DOS XCOPY or whatever.
You have to be careful if there is more than 1 partition on the 'master' pc you are using, as the enumeration of drive letters gets rather silly. You will do best to make sure the partitions have unique names before you start, as you can then see those names in explorer.
I suggest replacing a CD because they are usually master drive on the other IDE channel, so you dont also have to play with the tiny master/slave shorting pins. I've known some drives come without a bridging clip simply because master = no pins shorted! This makes it difficult to bridge pins to make the drive a slave....