Recently I installed Ubuntu parallel to windows, since I still have some projects to finish using windows software. While exploring the world of Ubuntu I came across Kubuntu, which looked very nice. Now I made the mistake to download the installation disk and install Kubuntu parallel to Ubuntu and Windows. I played around with Kubuntu for a while, it looks really nice but I decided to stick to Ubuntu. So now I would like to remove Kubuntu, but I don't know how. The same goes for Windows, as soon as I have finished my projects with windows software. I would like to remove it as well, so that finally my computer runs only on Ubuntu.

No matter what you don't really un-install an OS. You can do things like install over, delete partitions and more ways.

I'd just get the ubuntu that you want. Boot to that cd and delete any partitions. The installer ought to be easy enough to follow. It would warn you about deleting partitions.

Just be sure you don't want to save any data as it will be lost.

2 members found this post helpful.

This! + Fixing grub(even youtube has tutorials how to do it).
edit: If you want only Ubuntu then do reinstall and select "Use all disc(k?) space" when asked but backup your data before this step.
Also for future I want to inform you that Ubuntu and Kubuntu and any other *buntu is same Ubuntu with different Desktop Environment AND you can have as many DE as you want attached to one *buntu version you're using, just have to select them before log in session. Like if you keep Ubuntu and delete Kubuntu you can install KDE(DE that Kubuntu uses) for Ubuntu and XFCE(Xubuntu) and LXDE(Lubuntu) and also others like fluxbox, awesome, openbox,e16|e17 etc. To install them use Synaptic or Ubuntu software center or terminal(sudo apt-get install (something you like)). So next time don't waste time installing multiple *buntus on your box wasting media.

2 members found this post helpful.