It tells you about the issue. http://forums.cnet.com/5208-7587_102-0.html?forumID=69&threadID=301465&messageID=2813249
You'll also want Dell to tell you about the 10 or so drivers and what order to install them. Here's an example discussion -> http://forums.cnet.com/5208-7587_102-0.html?forumID=69&threadID=271360&messageID=2699006#2699006
It's far from trivial to install XP SP2 so don't guess. Get it from the horse's mouth.
I have a windows vista in my inspiron 1720 laptop. I wanted to install a windows XP instead but the installation process stops to tell me that a hard drive has not been found. what do I have to do?