It's definately SATA. Both HDs are plugged into "bootable SATA ports on the motherboard." Both HDs appear in BIOS screen, are detected at startup, and are present in Windows. Partition size on both HDs is 462GB out of 500GB, with 8GB always left over as unpartitioned space.
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Here is a clearer wording of my original post:
The Windows XP Installation refuses to format and install on HD 1 (plugged into SATA port 1). It just says that the partition is incompatible with Windows XP (even if the harddrive was not formatted in the first place) It will install on HD 2 (plugged into SATA port 2) just fine, regardless of what state HD1 is in. The installation will only offer to format HD1 and install on it if HD2 has already been formatted.
However, the installation ALWAYS refers to HD 2 as a system partition, regardless of whether or not Windows XP is or was ever installed on that drive. When trying to delete the partition on HD2, the installation will warn that it is a system partition- not so with HD1.
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This may be something as silly as the harddrive connected to port 1 is always defined as the system drive and therefore must always be formatted for any other drive to work as the OS drive. But by all indications, the harddrive that is this drive in my computer is on SATA port 2. I am not entirely familliar with how computers boot up, but it might have something to do with how a computer always goes to sector 0 of the harddrive on the first port of the mobo and from there it launches to the HD that has the OS (wherever it may be). That might explain why that one harddrive always has to be working for the other to have the OS installed on it. The problem is all the labelling seems backwards.
After an isntallation of Windows XP, HD1 is numbered as HD1 and HD2 is numbered as HD2, however in the XP installation, it always labels HD2 as C: and HD1 as D:. Also, HD1 appears at the top of the list and HD2 is second in the list. So by naming, HD1 is always first, and HD2 is always second, except functionality seems to be reversed.