Alfred,
From the hints provided, were you able to figure out how to get your system running again?
I remember when I had a similar problem installing Win 95 but that was the last time I had that problem and the solution I had to use in that instance was to install it using a floppy install CD.
After reading through the thread, I was going to suggest what Les suggested. My thinking is that perhaps the MB BIOS only looks at the primary IDE connector for a boot drive (HD or CD) so this is why you can't boot from your CD when it's on the secondary IDE connector.
Hope you get it sorted and when you do, definitely share how you resolve it.
I had to re-register a copy of XP Pro the other day, after swapping in a different motherboard. <img src="/forums/images/graemlins/scared.gif" alt="" /> I've never seen that before. When I called MS, they said that significant system changes sometimes require registering again. What a crock.
Well, not to get too far off topic but the PC world has really made it tough on Software Vendors to provide a serial number that users can use even after they've rebuild their server OS w/out providing a serial number that can be used on pretty much any PC.
The core of the problem is there is serial number associated with the motherboard that software can verify. So software makers simulate one using a combination of variables (system configuration plus Ethernet card ID, etc.). If you rebuild the system the rebuild will likely change this "calculated" serial number invalidating the software keys you originally were using.
Since Microsoft now tracks the registration numbers/keys, this is ultimately why you had to re-register your copy. The old one wouldn't work anymore because the soft s/n had changed because of your rebuild. <img src="/forums/images/graemlins/frown.gif" alt="" />