try installing through wubi (http://wubi-installer.org/ )...
It will download and install ubuntu 7.04. You dont have to make a cd and
burn it and partition the hard drive for that... you can just run wubi as if
it was any other windows program. It will install a whole new Operating
system (ubuntu or its derivaties). I did it that way and it a lot easier to
install the whole ubuntu that way..
When you restart after the installation there is a choice to run which
operating software to run... This way you can easily install ubuntu in a pc
without any harm done to your drive or windows...
try it

You need a high speed internet to do this ( if you have a slow connection
then i would suggest you to partition the hard drive and install ubuntu)