ubuntu without windows?

Yes, I have only Ubuntu and lot of other do to. 40GB is plenty unless you are wanting to save a lot of music/video files. RAM is the main issue. I think the minimum is 128mb but most recommend 256mb. If you have 512 or more even better. You can also use the Xubuntu variant that has lower system requirements.

The other issue is "being able to run certain programs". If you mean you have to use Photoshop or something else for your job then you will have problems. While there is a way to run some windows programs in Linux (it's called wine), it is not a perfect solution. If you have just that one app that you can't live without and it works with wine then great. However, it's much better to just accept that Linux is not windows and learn to use the apps that are available. There is almost something available to do what you want and when you learn how to think the Linux way you will fine that it's usually easier to find and install new apps than in any other OS. This page should get you started with install apps in Ubuntu -> https://help.ubuntu.com/community/SynapticHowto

Thanks for the help! I won't be using any sophisticated programs like Photoshop. The desktop I want to convert is for my dad, and he isn't that tech savvy.

Are there programs that are Windows emulators without having to have Windows actually installed?

And follow-up to my original question: How do I go about removing Windows, and will that mess up any drivers, etc. and create hardware compatibility issues?

Yes, you can run ubuntu whithout Windows installed!

But first, test your hardware! You can use the ubuntu Live-CD, which will not use your hard drive: http://www.ubuntu.com/getubuntu
Usually all your hardware is detected during the boot of the cd. Basic programs like word-processing, web-browsing, email, are pre-installed, and for more software you can use the tool: "Application -> Add/Remove..."
To permantly install ubuntu alone on the hard drive there is an icon "Install" on the ubuntu Desktop. Here is a guide: https://help.ubuntu.com/community/SwitchingToUbuntu/FromWindows
and this: https://help.ubuntu.com/community/Installation
Before doing that, backup all your data!

Here is another a guide to install a dual-boot (Windows/Linux) system: http://www.psychocats.net/ubuntu/installing

I gave my Dad an Ubuntu laptop. Seems to work fine for him.

"Are there programs that are Windows emulators without having to have Windows actually installed?"

Yes. The main one is called WINE but it's not really an emulator (Wine Is Not an Emulator), but it will let some windows programs run in Linux. It depends on the program. Check their web site if you want to know if a specific programs runs. You can also set up windows in a virtual machine but that is probably overkill.

"And follow-up to my original question: How do I go about removing Windows, and will that mess up any drivers, etc. and create hardware compatibility issues?"

Just boot the live CD and run the install. When asked about how to partition, let it use the entire hard drive and windows will be gone. Make sure you back up anything you don't want to lose. Ubuntu will install the drivers it needs for your hardware. This is not a 100% guarantee since there are some things out there that don't work well with Linux. Run the live CD for a bit first and see if everything works fine (like networking, printing, sound, etc.). If it does, great. If not you will have to do some research and see if there is a fix. There almost always is but it's not always easy.

Only the active Operating System looks after the drivers and the hardware, so on a dual-boot system Windows and Linux are independent from each other.

Yes, you can use Ubuntu without having Windows installed on your computer. In the installation process, you will get the opportunity to remove your existing Windows partition and make it available to Ubuntu. BUT DON'T FORGET TO BACKUP YOU DATA BEFORE INSTALLING UBUNTU IF YOU WISH TO KEEP THEM.

The minimum RAM requirement to install Ubuntu from the Desktop CD is 384 MB. But the more you got, the better it will run. For HD capacity, I just check my system and it says that I'm using 2.7 GB without my home directory (my personal data files).

Wow, min RAM has gone up since last I actually checked (5.10). I guess that only makes since with new features like compiz. However, if you are low on RAM Xubuntu is still a good option. Here are the requirements for the latest version (7.10) from the Xubuntu site:

"To run the Desktop CD (LiveCD + Install CD), you need 128 MB RAM to run or 192 MB RAM to install. The Alternate Install CD only requires you to have 64 MB RAM.

To install Xubuntu, you need 1.5 GB of free space on your hard disk.

Once installed, Xubuntu can run with 64 MB RAM, but it is strongly recommended to have at least 128 MB RAM."

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