So I was looking for an antenna cable in my cellar, when I found some old sweets in a by my old computer in a cardboard box. Two old PATA HDDs, a PATA CD-ROM and some IDE cables. That gave me an idea of installing one of the HDDs and the CD-ROM to my new desktop and install Linux on one of the drives (for dual booting). My motherboard is of the newer type, and has 6 SATA connectors, but only one IDE connector. The connector was labeled "PRI IDE". Does this mean that the device connected to it will be the primary drive? Why would it be labeled "PRI IDE" if there's only one IDE connector on the motherboard? I already have two SATA HDDs and one SATA CD-ROM/burner installed in my computer. Will a third one slow down the system? Also, the IDE connector on the motherboard and the PATA HDD is mounted at the bottom of the computer's housing, but the PATA CD-ROM is mounted at the top. The IDE cable has 3 connectors. The one in the middle is nearer the connector on the right than the connector on the left. I've read somewhere that the connector that is farthest away from the connector in the middle should be connected to the motherboard. Does it really matter which connector that is connected to the motherboard? Can I connect the connector that is farthest away from the middle to the CD-ROM and connect the two other connectors to the motherboard and the HDD?
"PRI IDE" means it will be primary on the IDE bus. It shouldn't harm your SATA bus at all. You can choose which boots first in the BIOS.
Historically, there were a lot of games played with IDE in the early days where you had to set slaves and masters and a bunch of crazy nonsense. Long and short of it is with modern BIOS, plug it in and use the the BIOS to tell what should boot first.
Can't answer the power question without more info, but in all likelyhood it should be okay.
It can mean two things.
First (and easiest) is that it is from the time where most motherboards had two IDE connectors on the motherboard. You could connect up to two devices per cable. Since only one device on the cable/bus could be active at the same time it was more efficient to put two harddisks on two different cables. Labeling them would be a nice touch. (But does not change anything. You could just use that cable on the secondary IDE port).
In the past the old setup was [Computer] [harddisk controller] [harddisk].
The harddisk controller was a separate and usually quite expensive card. That card interfaced with the computer (e.g. via the ISA bus in an IBM AT) and via cable(s) to the harddisks. (e.g. for MFM with 4 cable pairs. One to carry the analog data from the drive heads, one to control the disk).
Around that time some drives come on the market with the controller card integrated into the drive. We called it Integrated Drive Electronics. The connector on the drive was designed to directly interface with the AT bus, and another name for it was AT Attachement.
That controller was use to control a single drive an the setup would look like this:
[Computer with ISA ports] | [Connector card which was often called the HDD controller] (it was merely a device which changed the small 40 pin cable to a ISA bus form) | [Harddisk with integrated harddisk controller]
If you wanted a second harddisk you could plug in another of these so called 'harddisk controllers'. That was a waste. Later versions changed this to allow up to two devices on the same cable. You needed to tell (jumper) each device to tell it about the other devices. The modes were:
Setting the wrong mode would result in all sorts of trouble. E.g. If you have a single drive and set it to master it will (should) look for the slave and configure it. If there is no slave then it can keep looking forever. (Result: The disk hangs forever).
Later things got muddled because several manufacturers implemented smarted controls. As a result many drives use the same jumper setting for both "Master" and "single". Note that I said many, not all. Setting master mode on a single drive might thus work with one drive and fail with another.
A second 'helpful' addition is Cable select. The wiring on the IDE cable is used to determine if a drive needs to set itself to Master or to Slave. Those cable often have markings to indicate which one is the primary (aka master/single).
So much for the second option.
No. It will not slow down your other OS.
Whichever OS you install on the IDE drives might be a tad slower because those drives are older and most older hardware was slower than current hardware. It will not affect your other drives though.
If you have about 20 Watts left on your current power supply unit: Yes.
For precise figures: Check the power usage of the current system and read the label of the new drive. It should state how much power it uses. On average that is about 25-30 Watt at spin-up and about 15 Watt afterward.
In old motherboards with two IDE connectors, Primary is the first and Secondary is the second. Each connector accepts two IDE/ATAPI devices. The first (or single) drive must always be master (or single for WD hard disks since Master without slave doesn't work). The Master is always at the edge of the cable. If there is a second device at the same cable, then this is the slave which means that to accept or send data to the motherboard it must first get master's permission to avoid the two devices try to use the cable at the same time. The designations primary or secondary doesn't have an impact on Windows XP and newer operating system, but in earlier Windows and MSDOS, hard disk should always be Primary Master, otherwise one could face some incompatibility problems. Since the slave gets slower by asking the master for every data exchange, one good practice was to always connect the DVD-ROM as Secondary Master so it could work at full speed independently from the hard disk.
SATA interfaces support only a single device, so it is always a "master" and works at full speed (depending on SATA version, since SATA III device would be slower on SATA II interface).
New motherboards have a single IDE interface, so there is only Primary master (first device) and Primary slave (second device). Most newer chipsets do not support an IDE interface directly, so be careful as it might be attached to a RAID controller. This means that you might need some drivers in order to install Windows (or whatever), otherwise they could not be able to see the IDE devices. In Windows XP for example, you press F6 when you see the relevant message on screen and provide the driver in a floppy disk. In Vista and 7 you can browse to a different path or USB device containing the necessary driver (thanks God, as newer motherboards do not have a floppy controller!) For Linux the necessary driver might be included in the DVD-ROM so you may not have problem seeing the IDE hard disk to install Linux there...