Step-By-Step Instructions to Create a Dual-Boot System

Okay, now that I've sufficiently confuzled you, here's the simple, step-by-step version of my advice.

I'm going to assume that you're using one big hard drive, which will be partitioned into three sections: One for the Windows system, one for the Linux system, and one big partition for shared data. If you want to use multiple hard drives or some other partitioning scheme, you can ask for specific advice in the Forum.

1. Use a big hard drive (at least 500 GB is recommended - 750GB or 1TB would be even better) so each system will have plenty of room, and there will be plenty of room for documents and data.
2. Windows will be installed on the first partition because that's where Windows wants to be installed, and it gets cranky when it's installed elsewhere. (Linux, on the other hand, is more laid-back and doesn't care very much where it's installed.)
3. Boot to your Windows installation CD with the drive unpartitioned. When you get to the part where Windows wants to know where to install itself, create a single NTFS partition at the beginning of the drive.
   
   
   If you're going to be creating a separate data partition (which I recommend), then a partition size of 100GB should be enough for Windows and its programs. But if you plan to install a lot of games, desktop publishing, graphics design, or Web development applications, you probably should make the Windows system partition a little bigger because those type of apps tend to be big and to include a lot of graphics files in their program directories.
4. Let the installer finish installing Windows on the single partition you just created.
5. After Windows installs and reboots, activate it, install any additional needed drivers, and download all the available Windows updates. This may require quite some time and several reboots. (You can wait until after the Linux system is installed before installing the Windows updates, if you like; but then if Windows vomits on an update, it may be harder to fix once the dual-boot configuration is in place.)
6. Once all the updates are installed, from within Windows, create a new partition on the hard drive for the shared data and give it a name (like "My Stuff," for example).
   
   
   Make this partition big. How big? Well, basically subtract the space you'll need for your Linux installation from however much space is available on the drive, and create a partition of that size. So if you have 400 GB of free space, and you want to give Linux 100 GB, then make the shared data partition 300 GB.
7. When the new partition has been created, map your libraries to the new partition. This will establish the new partition as the place to store your stuff, if you do it correctly.
8. Reboot the machine into Windows and log into your Windows user account. Wait until the machine hascompletely started, and then shut it down. This is to insure that the changes you just made have been saved to the registry.
9. Boot into your Linux installation CD or DVD. There will be some obvious link or button to click to install Linux. If you're pretty sure that all your hardware is supported in Linux, then just click that button. If not, then look for a link or button that says "Try Linux," "Run Live CD," or some such thing. If available with your distro, this will boot Linux without actually installing it. (This option is available with Ubuntu, Mepis, Knoppix, Fedora, and many other Linux distributions, but not all of them.)
10. Once you have decided to install, start the Linux installer.
11. Early on in the installation process, the Linux installer will ask you where to install Linux. You'll be offered several options, one of which should be to use the unused hard drive space. That's the option you want.
12. You'll be asked what Linux partitions you want to create. Unless you're already familiar with Linux partitioning, I suggest you create only two: "/" and "swap." The swap partition should be at least 1.5 times the amount of installed RAM. The / partition should consume the rest of the unused space.
    
    
    Unless you're an experienced Linux user with a reason to want a particular file system, I suggest that you use whatever default file system the distribution recommends for the / partition.
13. You probably will be asked to create a "root" or "administrator" account and password, and a user account and password. Make your user account name in Linux the same as you chose in Windows, and you have a better chance of the installer finding your Windows data partition.
14. If the installer recognizes the shared data partition you created under Windows, and offers to make it available to you in Linux, say yes. If it doesn't, no big deal. You can link it later from within Linux.
15. At some point you will be asked to configure a bootloader (usually LILO or GRUB) and write it to the MBR. The most important thing to do here is to make sure that the bootloader the installer is proposing has recognized and offered to boot both your Windows and Linux systems. This almost always happens without a hitch, but make sure anyway.
    
    
    By default, the bootloader usually will include other options, such as booting into Linux repair mode, or the CD or floppy drive. Leave those options in place, as well. They could come in handy.
16. You also will be offered the option of which system should be the default operating system. Most times, Linux will choose itself, but you can override it if you like. The default operating system is the one that will boot if you turn on the computer and do nothing else. (When you want to boot to the non-default operating system, you just have to hit the up or down arrow button on your keyboard to highlight the OS you want, and then hit enter.)
    
    
    Finally, you'll most likely be offered the option of how long the system should wait before booting the default OS. The time the installer will suggest may range from ten to 30 seconds. That's how much time the system will give you to decide whether to hit the up or down arrow to override booting the default OS.
17. Once you're sure that the bootloader recognizes all of the systems and that the options are what you want, click the button or link to "write," "save," or "commit" the bootloader to the MBR.
18. Depending on your Linux distribution, there may be some other steps, which should be quite self-explanatory. Once the installer announces that it is finished, remove the installation media (if instructed) and boot into Linux. Log into your account and download whatever updates for itself it finds, then reboot back into Linux to make sure that any changes have been fully configured.

And that's that. You now have a dual-boot, Windows / Linux computer. But there are some caveats.

If at any time a Windows update, service pack, or repair install overwrites the MBR with its own bootloader, you will no longer be able to boot your Linux system. In the past, we used to create emergency boot floppies to fix this problem. Nowadays, most Linux distributions include this functionality on the installation CD or DVD. It's usually called "Repair Mode" or some such thing, and one of the first things it looks for is a broken bootloader.