I have Windows 7. I want to run Ubuntu inside it and don't want to loose any data.. How can I do this?
Besides VMWare and Virtualbox, there is the Ubuntu Wubi installer.
You need to download and install Vmplayer and also download an ubuntu ISO . You then need to build a new virtual machine while providing it the ubuntu ISO . After installation allow VMplayer to install VMTools to enable feature like copy paste and drag and drop across the virtual machine and the host.
If you get VMware (Player or Workstation), you can get a pre built Ubuntu machine and you won't have to go through the hassle of installing it your self (even though its pretty easy)
Also, the Linux Machines should be free of charge (I don't see any paid ones)
refer to this link http://www.psychocats.net/ubuntu/virtualbox for running linux inside windows 7 or any Microsoft based operating system