I have 3 500gb hard-drives installed....

Couldn't you technically install seperate OS's onto each hard drive, and just change which one you boot to in the BIOS when you want to switch?Zeke129

[QUOTE="Zeke129"]Couldn't you technically install seperate OS's onto each hard drive, and just change which one you boot to in the BIOS when you want to switch?Phantsy16

http://www.osloader.com/

read through the description on that page. 

[QUOTE="Zeke129"]Couldn't you technically install seperate OS's onto each hard drive, and just change which one you boot to in the BIOS when you want to switch?Phantsy16

Nope. What you do is install the ssecond OS on the second HD. Then when you boot up. you'll be taken to a DOS screen asking you which OS you would like to boot into(For me its windows vista as one choice and "older windows OS" or sumn like that, which is XP as a second choice) Choose what you wanna boot into and it boots. You only have a few seconds to choose though otherwise it automatically boots into the most recently installed OS. This will happen every time you boot up. I know from experience, its what i do.

When you install a second OS, the boot loader on your first drive is modified to take into account the other OS. You don't have to do anything.Gog

[QUOTE="Gog"]When you install a second OS, the boot loader on your first drive is modified to take into account the other OS. You don't have to do anything.theragu40

It can be done on separate drives. That's how my computer is set up, actually (XP on one drive, Ubuntu on another).  

[QUOTE="Gog"]When you install a second OS, the boot loader on your first drive is modified to take into account the other OS. You don't have to do anything.theragu40

I think you can

Install Xp to primary HDD & Vista to Secondery HDD(Example). 

If you install Vista to your secondary HDD it will modify your primary HDD's some files (I don't know which file).

But I Not Sure 

Ok i will list it all.

If u have only 1 hard disk, then u have 2 have at least 2 partitions, install XP first partition and install vista on the next.

then when when u will boot up your pc u'll get 2 choices either windows vista or earlier version of windows (XP).

if u got 2 or more hard disks. there shouldnt be any problems with which os you should install first, install vista on hard disk 1, xp on hard disk 2.

then if u want to boot xp select the first boot device to hard disk 2, if u want to boot vista choose the first hard disk as the primary boot device.

to me i just have to press f11 to choose from which device the pc should boot.

[QUOTE="Phantsy16"][QUOTE="Zeke129"]Couldn't you technically install seperate OS's onto each hard drive, and just change which one you boot to in the BIOS when you want to switch?Miguel16

Nope. What you do is install the ssecond OS on the second HD. Then when you boot up. you'll be taken to a DOS screen asking you which OS you would like to boot into(For me its windows vista as one choice and "older windows OS" or sumn like that, which is XP as a second choice) Choose what you wanna boot into and it boots. You only have a few seconds to choose though otherwise it automatically boots into the most recently installed OS. This will happen every time you boot up. I know from experience, its what i do.

Yes you can do it with 2 drives. RThere will be NO problems