That can happen under a few conditions.

1. Windows XP was freshly installed. No service packs.
2. Continuing on item 1, the Dell drivers have not been installed.

No need to write how to install these. Dell documents it as well as thousands of posts.

If that fails, read the Storage "Lost and Found Forum" Sticky post at http://forums.cnet.com/5208-7588_102-0.html?threadID=354911&tag=forums06;forum-threads

That covers all the usuals, the recovery methods and more.
Bob