So how big is a Linux installation? How much of my drive will it take up?
I don't know if this is going too much off-topic. Many questions are answered on the Ubuntu website, for instance:
http://www.ubuntu.com/products/WhatIsUbuntu/desktopedition
https://help.ubuntu.com/8.10/index.html
https://help.ubuntu.com/8.10/installation-guide/i386/minimum-hardware-reqts.html
Note that Ubuntu is not the only Linux distribution, but it is well-known for its user-friendliness, and the high probability that things 'just work' without problems. And maybe you like the idea that it is founded and sponsored by a South-African multi-millionaire.
I'm not sure how to boot from a CD rom. This has nothing to do with Linux, but I want to format the drive of an old computer using Windows ME. I stick the ME recovery CD into the computer, and boot from the CD, but then I am presented with a command line type thing, which I have no clue with.
To boot from the CD-ROM, the CD-ROM needs to be in the drive before the computer boots from the harddisk. Also, the BIOS needs to be set up to boot from the CD-ROM before booting from the harddisk, but often this is already the default.
When you boot a computer with the CD-ROM inserted, the CD-ROM starts humming, and the computer clearly boots in a different way than without the CD-ROM (e.g. you get a command prompt instead of windows), then you clearly succeeded in booting from the CD-ROM.
I'm not really sure what a windows ME disk is supposed to do. Maybe it gives you a DOS prompt.
In that case, formatting a harddisk can be done with 'format c:'. If you have multiple drives, and you don't want to format all of them, make sure you use the right drive letters. The drive letters can be different when you're booting from the CD, so you might want to check the drive contents (e.g. 'dir c:') before formatting it.
I think a windows ME bootdisk is supposed to have a setup program called 'setup.exe'. You can check that with the command 'dir'. If it's there, you can start it with 'setup.exe' or 'setup', to install windows ME.