Of course, you disconnected that external while changing the internal drive and reinstalling XP? Not that it should make a difference, but it's kind of an extra precaution. In that case, it can't be related to anything you did on that PC.
But it seems you didn't realize that having your data only on one external drive means you didn't have a backup. And not having a backup (a second and preferrably a third copy) is risky, as you notice now, especially if it's on a device lke an external hard disk, which are notoriously unreliable for some reason.
That being said, things you can try are:
1. See if the disk can be read on another PC. Unlikely, but you never know.
2. If not, try the recovery tools discussed in the top 2 posts in http://forums.cnet.com/storage-forum. But it really is a good idea to buy a second (identical or bigger?) hard disk first and make a clone of this corrupted external disk first and try those recovery tools on the clone. After all, the original is all you have, and you don't want to mess it up even more. Although, using the demo mode or a read-only mode on the original to see what the tool can do won't harm. But don't let it do any update on the original!
3. If no luck, it's time to find a professional data recovery company. But it's not unlikely that one of those DIY tools (I'd start with Recuva) find a lot, if not all.
And just a note. You do know that you need XP SP2 at least to be able to read such a large hard disk? If the issue is that you didn't yet install SP3 and are working with the original XP or SP1, the disk might be readable in another PC with Vista or higher.
Kees
Kees
I had to change my booting internal hard drive because it was not working. The new Internal HD has installed ok & is working (I have reinstalled Windows XP - eventually I may use a Linux distro) BUT the external HD (a Seagate 1TB) that I had saved ALL of my files & documents on as backup to use when I got the PC back up working is now showing as 'RAW - you need to format your drive'
I need help- is this a common occurrence when a new Internal HD is installed & the OS re-installed? Can I try it in a different PC? What can i do?

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