Hi René-Frank,
from talking to you earlier today, you are using the two SATA drives on your Dell PC in one RAID virtual drive so as to get superior performance. This is always a great idea in Photoshop for the repeated access to the drive. The RAID should be made for the scratch disk and not for the system software and the PS CS program.
What you have done is likely had Windows XT repair something when you rebooted. In any case, it's a great risk to have a RAID for you only copy of your files and your software!
My suggestion is to take advantage of your Dell service. With their guidance, (or the tech who is near you) add your new spare SATA drive to the computer and make that your system software and program drive. That means that Windows XT and Photoshop will reside there. Use the two raided drives for "scratch" for PS and virtual RAM.
Throw away whatever you don't need but make sure you have a backup of your pictures. As a start, you can keep one copy on a separate partition on your new boot drive. So you might allocate, for example, say 100 GB of your new drive just for storing copies of your precious files. At the same time, I'd burn DVD's, 2 copies and have them stored in two different places outside your home!
I was in San Francisco at the Shochet Photography Store. I met a long time photographer, a young middle aged fellow, who's apartment was destroyed by fire. He stored his DVD's on top of his computer. He lost his original film and the files from the hours spent scanning his life's work!
Asher