I want to install Ubuntu 13.10 on my pre-installed windows 7 pc and I want a dual boot. I have no empty partition on my hard disk drive. I don't want to re-install windows 7. How should I do it? Please answer in steps. Also suggest the amount of space I should allocte to ubuntu 13.10.
You can install ubuntu using the Wubi installer. It will install ubuntu next to windows on the same partition without deleting it. You will be able to choose your preferred OS at boot.
The other option is to make a dedicated partition for linux if you have free space on your hard disk. You can make an unallocated space with the built in windows partition tool. Than you can boot the installation disk/usb drive and make a linux partition and install linux there. Linux will make you automatically the grub bootloader where you can choose which os you want to boot at startup. Although If you uninstall linux you will have problems booting up windows as grub will also be deleted, but it can be solved with a windows installation disk and a few line of commands.
But you don't need to uninstall windows either way.