I've got an MSI K8N NEO Platinum motherboard, I just bought a Maxtor Diamond Max 10 300 GB SATA hard drive. I was wondering how to slave my old PATA drive to get the files off. I had heard somewhere else not to attempt this because windows gets confused and doesn't know which drive to boot from.
The MSI boards don't have an option to boot from "HDD1, HDD2, etc". What you have to do is this: disconnect the old drive from the system. Install the new hard drive and install windows. When windows is done, reconnect the old hard drive. The BIOS will remember which drive has windows on it and boot from it. However, sometimes it won't. In this case, Windows will ask you which copy of Windows you want to boot right after POST. You won't know which drive has which copy of windows until you pick one. After picking one, if the old copy of windows boots, then reboot and pick the 2nd one- which will boot you into the new windows/hard drive. Once that's done, copy the files off the old one in explorer and format it. :-)
If all that still doesn't work (I.E. computer refuses to boot from new drive with old drive installed), buy a USB hard drive enclosure. Boot windows on new drive, connect old drive via USB, copy the files, and format it.