I also did the "downgrade" on the 5315. Fortunately (after trying only
3 different copies of WinXP install disk), I started looking around to find out why they weren't working. When I did I found the following link:http://soulpass.com/2007/11/10/insta...5-2153-laptop/
It tells how to install the proper SATA drivers into your own copy of the XP install disk. After this is done the installation works without a hitch.
It also tells how to install all the needed drivers, AND includes a couple of zip files with the drivers that are needed. So even if a person decides to not install the SATA drivers into the XP install disk, the link is still a great "one-stop-shop" for downloading all the required drivers.
Thanks to that one link, I was up and running XP in very short order. Hopefully, by posting the link others may see it and benefit from the wisdom of one who is much wiser than myself.
One small note, I've glanced around at other postings on this topic all around the net, and some people are suggesting to change the BIOS settings in order to get the XP installer to see the HDD. I would advise against this because other people (again, ones much wiser than myself), have said that this can cause problems with both potential data loss/corruption, and slow the HDD xfer speeds considerably. Your own experiences may vary, but given how the above link makes the whole process relatively simple, then why not go ahead and install the needed SATA drivers into the XP install disk and that way there's no potential for harm.
Anyway, Best Regards and I hope this helps someone.