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I have one CPU (Complete Setup Box) in my desktop, and need to run two operating systems. Instead of installing them both on the same hard drive, I am thinking of adding a second drive.

Is it possible to have two different hard disks with two different operating systems depending on one CPU? If so, what additional components do I need to include?

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You're confusing Central Processing Unit and Computer Case.

In general, it is possible to have multiple hard disk drives in single case. The 3 main limiting factors are number of HDDs that the PATA or SATA controller supports, number of empty HDD bays in the case and number of available power connectors.

To check if your computer has met the requirements, you'll have to open the case and take a look inside.

Here's a picture of traditional SATA power connector

SATA power cable form wikipedia

You should be able to find at least one free cable with such end in your case if your computer uses SATA.

If you have an older computer, HDDs will probably use older Molex connectors such as this one:

Molex from wikipedia

Here's a picture of SATA data cable and port on the motherboard: SATA ports from wikipedia

You should have at least one port available on your motherboard. It could happen that cable is missing. If that's the case, you'll need to buy one, but they are usually cheap.

If it happens that your computer is older, it could be using PATA connectors.

Here's image of PATA port on a motherboard (the two bottom ports with pins going sticking up from them): PATA from wikipedia

and here's image of a PATA cable:

PATA cable from wikipedia

For the free bay, the best way to look would be to find your existing hard disk drive and see if there's a bay of that size available.

Here's image of typical hard disk drive:


It could happen that there are no free bays for the HDD. In that case, find your optical disk drive and see if there are free bays of that size. There are mounting kits available which will allow you to put a HDD safely into CD-ROM drive sized bay.

Do note that it could happen that you have both PATA and SATA ports. In that case, try to get a SATA HDD, because they are generally faster than PATA and will be easier to replace in case of failure.

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So, you say that this is not possible ? – Chok May 25 '11 at 21:56
Well, i really dont have enough money to have two different computers one with Development OS and another with Server OS – Chok May 25 '11 at 21:56
@Chok No. I said that I don't know. Take a look at the update. I put images of what you should look for in your computer. Most likely, you'll have room for at least one more HDD, but it's not uncommon to have room for several more. – AndrejaKo May 25 '11 at 22:07
@Chok; It is perfectly possible to run two seperate OS' on one machine - this is called "dual booting". If you wish to run both at the same time, this cannot be done as you can only run one operating system at once, however Virtual Machine software will allow you to run a virtual OS which can perform the same functionality. – Phoshi May 25 '11 at 22:10
@Andrejako Thank you for your screenshot explaination – Chok May 25 '11 at 22:18

There is no problem unless you want to run both of them at the same time (operating systems that is, not drives).

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No, i dont want to run both OS at a single instance. But how to achieve this. I am totally new to this Hardware assembling. Do i need Raid controller ?? Can i have two different hard disk like one on 250 GB 7200 RPM and another on 160 GB 5400 RPM – Chok May 25 '11 at 21:54
You don't want raid unless you want to use RAID for backing up the drives. Just stick them into the motherboard and that's about it. Does not matter that they are different sizes, speeds, etc. – soandos May 25 '11 at 21:55
So, let's assume that i have two different hard disk with one CPU. Now, when i start the computer which hard disk will popup as Default and if i need to switch to another Hard Disk .. How should i choose ? – Chok May 25 '11 at 21:59
Whichever one you want to. You can change these settings in BIOS, or depending on your bootloader, through that (boot.ini for winXP, Grub for linux, etc) – soandos May 25 '11 at 22:00
Okay, i am able to understand. Every time, i need to change the Hard Disk - I just need to restart and then go to BIOS - From where i can chose which Hard Disk i need to go !! – Chok May 25 '11 at 22:01

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