There is a wizard in the regular live desktop Ubuntu install CD which will ask you if you want to install Ubuntu along side other operating systems like Windows or use the whole drive for Ubuntu. The wizard will let you choose how much space you want to use for Ubuntu. The bare minimum amount of free space for Ubuntu is 5GB free space, but I recommend using 20GBs or more for Ubuntu just in case you want to install more 3rd party software like Filezilla, VLC, and Audacity in Ubuntu.
You first have to install Windows if it is not installed yet. Secondly, you start your computer from the Ubuntu Live CD, and You have the option of installing Ubuntu along side other operating systems, or using the whole disk for Ubuntu.
It is recommended that you defrag your Windows drives before you install Ubuntu to prevent data lost.
Back up your important files just in case something goes wrong.
You can also use the WUBI.exe (Windows Ubuntu Installer) to install Ubuntu on your Windows partition, and Wubi.exe will take care of setting up the dual boot, and boot selecter program. Wubi.exe is found on the desktop version of the Ubuntu 10.10 install CD which you can access within Windows> Computer >Ubuntu install CD to run Wubi.exe to install Ubuntu a long side Windows without risking messing up your Windows partition if something goes wrong.
However, Wubi.exe installs of Ubuntu 10.10 are slightly slower then actual installs of Ubuntu from booting to the livecd since wubi.exe virtualizes the Ubuntu drives on an NTFS or FAT partition which is slower then EXT file system drives which is faster.
Easiest is to have Win7 installed first, then follow the steps when trying to install Ubuntu. Its easily detailed and even easier to follow. Or like mentioned above, try installing it in windows first to try it out. Just run the WUBI installer. Cheers!
You could try doing it with wubi auto installer, if I recall the only feature missing going that route is no hibernate but its been a while since i used it.