It sounds like your diagnostics partition may be missing or corrupt. If you repeat those instructions without using the F10, are you able to get back to your regular Windows?
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I just found a review of the P-173-XL
***here***.
It says
The P-173XL FX also offers a high level of performance in its storage thanks to the use of dual 200GB 7200rpm hard drives. On their own, they offer some decent performance but Gateway has linked the two together in a RAID 0 array that makes for a larger single storage device that has performance much more in line with that of a desktop drive than a traditional notebook setup.
RAID 0 is a terrible choice. Using it means that if either hard drive goes bad, you lose all the data on both drives. So if one of the drives developed a problem in an area that was storing data for the diagnostic partition, you'd get a problem like the one you encountered -- and it probably wouldn't show up until you tried to boot into the partition.
So it may be that one of your hard drives is failing and developing bad sectors, or it may be that the problem always existed and you never encountered it before because you never tried to access the diagnostics partition before.
As long as you can get the laptop to boot into your Windows partition instead of your diagnostics partition, you may be able to get back into Windows. This won't fix the whole problem, but it should allow you to get your data off the computer.