There are two ways you could go about this:
Option 1:
Either boot the PC to BIOS (pres DEL on boot), and select a boot device that is not the HDD - preferably a DVD drive. You should then insert a Windows installation DVD into the DVD drive and boot the Windows installation. This installation will prompt the opportunity to reformat or repartition your HDD.
What devices are available on the PC? When I go over the specs from Dell, I see that all CD/DVD/Floppy/USB drives are optional, so what drives are actually available to you? If you do not have a DVD drive, you may need to boot to an image of the installation DVD on a USB drive.
If you select this option, I could easily guide you through it. This would format the HDD, but keep the HDD in the PC. You would then have to move the actual HDD to your other PC in order for it to be connected to your motherboard and turn up as another disc on your system.
Option 2:
Remove the HDD from the PC. Install it in your primary PC.
When connected, boot to BIOS (pres DEL on boot) and check if the HDD is recoqnized.
If it is recoqnized, boot to Windows. The HDD will show up as a listed X: (X being whatever ID your system gives your HDD).
Right click --> Options --> Functions --> Format.
Easy.
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Did this help, or have I misunderstood what you are trying to do?