As I know, there are many ways to use Ubuntu(Linux) our laptop or PC.
Firstly, if your HDD(harddisk) is new or clean one and there are two or more partitions on it, you can use dual OSes with it: eg, Window OS and Linux one. One OS is running at a time. In each partition, each OS is hosted. When PC is started, Window Boot Manager shows OS selecting menu on very first page to choose a desired OS. We can’t switch to another OS when using a specific OS is running.
My prefer method to install Ubuntu(Linux) is installing via bootable Live USB. The steps are so easy to do so. Just go http://www.ubuntu.com/download/desktop and get ubuntu OS’s “.iso” file. Then, by visiting to http://unetbootin.sourceforge.net/ and get unetbootin software. Run unetbootin software on your laptop or PC. Then point out the desired USB (assumed that a USB(at least 4 GB capacity) is already assembled in PC, it should be formatted by FAT32, be aware that it’s with FAT32) and downloaded .iso file. After that, you will get a bootable USB to install Ubuntu OS.
Open the PC or laptop that you want to install Ubuntu(Linux). Already assumed that you changed boot sequence to “Removable Device” in BIOS setup. Then it will automatically loaded Ubuntu OS and will make installation automatically by just following on screen instructions. Then you can start using Ubuntu OS on the fly.
Next, you are a Window OS user. Let’s say that your HDD has only one partition and Window OS is already running on it. At that time, you want to start using Ubuntu(Linux) OS. OK fine, there is another alternative way for you. You can use “Wubi Ubuntu Window Installer” at http://www.ubuntu.com/download/desktop/install-ubuntu-with-windows.
Just run “wubi” to install Ubuntu. After following on screen instructions, you will find dual OS on start up screen when PC is opened. You can find your Ubuntu OS as a disk image file on hosted Window OS.
Another option is if you want to use parallel OSes, you should use Virtual Machine or Virtual Box(installed Ubuntu OS) on Window OS. Just be aware that your machine’s memory is parallel exhausted by parallel OSes at that same time.
That’s all. Enjoy!!!