Even if "Original", the point remains WHICH version? You're referring to the COA Key "Sticker" when you speak of "serial #" I "assume"? An OEM PC (what you bought) should have that on it. To "hack" that properly to work will require some other resources not available on MSFN (a big no-no). There ARE threads on the subject on MSFN -and- information on the WWW provided you search hard enough.
Hints (re - your "CD") - posts #25, #28, #32 (ignore "dross")
As Fernando1 said, if it won't work with the Drivers integrated, it's perhaps not a "clean" "CD" and has some additional mods in it. I believe he ALSO said that you NEED to ensure that it has SP2/SP3 Integrated and Driver Integration would be unnecessary.
I believe that's IF you don't have SATA controller listed (which you DO have listed).
Now, going BACK to the Post #1 of this topic
a ) Make sure, that the "Textmode driver" Mode is enabled.
Are you following the Instructions TO THE LETTER? You might ALSO note the explanation of AHCI/RAID (SATA) vs IDE (PATA) in the BIOS (if changeable).
and pick your version of GX250. then look in "Advanced Features" (BIOS settings) - the SETUP portion indicates
Drive Controller - Configures the serial ATA controller's operating mode.
Normal enables the serial ATA controller to operate in its serial ATA native mode only.
Compatible enables the serial ATA controller to operate in serial/parallel ATA combination mode.
SATA Operation - Configures the operation mode of the integrated hard-drive controller.
Normal — The hard-drive controller is configured for native mode. This mode provides the highest drive performance and most flexibility.
Combination — The hard-drive controller is configured for combination mode. This mode enables compatibility with some older operating systems that do not support SATA drives.
The factory default setting is Normal.
NOTE: Changing this setting affects the order in which drives are listed. However, system setup does not reflect these changes until after a reboot.
If you are running any Windows OS with your Dell GX520, please open the "IDE ATA/ATAPI Controllers" and - if applicable
What did work was Win 7 install
So this is (apparently) how you obtained the VEN_DEV info. Now, go BACK (again) to Post#1 and select the CORRECT DriverSet - and notice that Dell has a slew of Drivers listed here -
Finally, you're touching on a subject (the "no-no") that violates MSFN rules ("downloaded"). We CANNOT confirm/deny your "CD" accordingly. Be forewarned!