You can get an IDE-to-USB interface, then connect it to your desktop via USB cable. It doesn't matter whether there's an operating system on the hard drive, it will be formatted as an NTFS file system, you just navigate to the files you want and copy them to your desktop's hard drive. Quite simple, really.
Here's an example of a cheap adapter, even if you aren't in the U.S. and can't order from Newegg, at least you know what you're looking for:
I have one of these, and yes, it'll work for any IDE drive. There hasn't been a change to the IDE spec for quite a while. I don't think many have been making them or buying them much for the past few years. ATA100 is old. I have used it on ATA100 drives.
if the laptop still boots into windows you can turn on file sharing on windows xp and then move her files from the laptop to the desktop over the network. they also make usb laplink cables and software. the real easy way is pick up a large usb data stick and just drag and drop her files onto the usb stick then onto the desktop.