"no root folder is defined" during installation process

[xihad76]

hi, i m new here in this forum and very much interested to use ubuntu in my pc. so i tried to install ubuntu 8.04 from windows installation and in a seperate drive apart from the drive where xp is isntalled. after completing installation it tells me to reboot without dvd and i did so. then entering to ubuntu after a certain period during installation process it says "no root folder is defined. please correct it from partioning menu." if i press ok, it still continue showing me the same message. so i had no other way but to press the restart button.

so what is the problem here? can anyone plz help. i have no past experience of using any version of linux.

thnk u in advance.