Oh, dude, freeing up disk space on Ubuntu is like decluttering your room but with less physical effort. You can start by removing old unused packages with the 'sudo apt autoremove' command, then clean up cached files with 'sudo apt clean'. If you're feeling adventurous, you can hunt down large files with the 'du' command and delete them. Just be careful not to delete anything important, like your collection of cat memes.
disk space analyzer
GNOME Disk Usage Analyzer
You will have less disk space available for OSes.
If by "Cleaning up" you mean "deleting data" then space Will free up.Defragging or "Checking Disk" will not create free space.
Ubuntu uses the ext4 file journaling system, which doesn't get fragmented.
dynamic space
Yes, it can be done from the windows installation disk, but it's cleaner if you remove ubuntu with the ubuntu live cd and then install windows.
Well, if you have a DVD burner drive, which is pretty much standard on computers today, you can just download the Ubuntu ISO image and burn it to disk without a fuss. There used to be a program called ShipIt that would send you a copy of Ubuntu free of charge, but Canonical shut it down. Otherwise you'll have to spend a (Nominal) amount of money to buy a copy from sites like Distro Watch.
Recent versions of Ubuntu Linux require about 5GB of space.
Ubuntu is a free system program. Therefore, all of the software which comes from Ubuntu is free as well. One might want to check out from the main website of Ubuntu.
No. After download and burn the Ubuntu 10.10 install disk, you can either TRY Ubuntu without affecting your Windows at all, or INSTALL Ubuntu to have them both in your PC. However, to install Ubuntu, you need to be careful. Make sure not to install Ubuntu to the Windows drive. That is all.
Ubuntu is a free, supported debian/linux implementation of Unix. As such, you can do nearly anything that you can do in Unix in Ubuntu.