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I am able to try Ubuntu 13.04 using a live usb. However, when I attempt to INSTALL UBUNTU... I am told that no existing OS is detected on the hard drive.

When I get a new laptop, I do intend to format this one and use it purely for Ubuntu. However, in the meantime, I would need the ability to dual boot.

I do select the other option, to partition the drive... From inside Windows, I had shrank the C: volume and created a new partition w/ 5GB of space (for some reason, I could not shrink it any further although I have 90 GB of free space left)... In Ubuntu, I selected this 5GB volume as reserved bootable BIOS space.

However, when I attempt to continue, I am told that no ROOT file space has been selected.

Do I need both reserved space for BIOS and ROOT space? Or should I only use the free 5GB for the ROOT space?

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You do not just need reserved BIOS space for Ubuntu. You should also have at least 10GB of ROOT space. ROOT space is like the C:\ drive on Windows. It is where Ubuntu is actually installed. This partition will be formatted, so be sure you know what you're doing.

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You may need to defragment your C: partition and/or temporarily disable the page file in Windows. (Googling on the latter turned up a bunch of pages, most of which said not to disable the page file. That's perfectly good advice for normal conditions, but doing it temporarily may enable you to shrink your C: partition more than you can do it now.) Also, you should NOT create Linux partitions in Windows! You seem to have gotten lucky this time, but creating new partitions in Windows frequently converts all the partitions from "basic" to "dynamic" form, and Windows dynamic partitions use a proprietary format that makes it difficult or impossible to install Linux on the disk. Thus, whatever you do, DO NOT create more partitions in Windows. If you need to create more partitions, do so using a Linux tool.

Once you've freed up more space, you need to use the Linux installer (or a Linux emergency disc and a tool like GParted) to create your Linux partition(s). In the installer, you must mark one partition as the root (/) partition; that's where Linux goes. If nothing is marked as the root (/) partition, it's like telling the moving company you've hired to move all your stuff into the house while you point at an empty field -- they'll scratch their heads and ask what house (root partition) you mean.

The default Ubuntu installation uses a root (/) partition and a separate swap partition, the latter being as much RAM as you've got or a bit more. (It's used in suspend-to-disk operations or if you run out of RAM.) I recommend creating a 10-30GiB root (/) partition, swap, and using the rest as a separate /home partition. If you want to give Linux less than 20-30GiB, though, a separate /home partition may not make much sense. The advantage of a separate /home partition is that it keeps your user data separate from the OS data. This can simplify certain types of disaster recovery and re-installation scenarios.

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