For anyone else contemplating this move, it turned out to be a piece of cake! My builder had had the misfortune of previously running into this rare problem and thought I might also have problems. My old hard drive was installed as an IDE slave and is recognized by My Computer as drives F, G and H (the three partitions of my old Win 95). Drag-and-drop from the old hard drive installed as an IDE slave (FAT file system) to the new C (NTFS file system) works just fine. A pleasant surprise on my new computer was learning my MP3 jukebox would play with no changes on XP's Media Player.
(I found this on Microsoft's support. Apparently a Western Digital drive can cause problems if used as a slave in an XP Pro system.
http://support.microsoft.com/default.aspx?scid=kb;en-us;812581SYMPTOMS
When you try to configure a secondary hard disk on your computer to be a subordinate (also known as slave) drive, you may receive the following error message:
There was a problem installing your hardware,
Code 28 one of the Filter Drivers installed for this device is invalid.
CAUSE
This issue occurs because filter drivers for certain types of hard disks are not valid for other hard disks. This issue is most common when you install a Western Digital hard disk as a subordinate drive in a computer with a different manufacturer's hard disk is installed as the master drive.)