There are different versions of Ubuntu for different purposes, different types of computers and the requirements of hardware, particularly RAM are also different. The Ubuntu Server (CLI) Installation only requires 128MB while the recommended requirement for the Ubuntu Desktop Installation is 1GB of RAM.
During an installation of Ubuntu, it will tell you during the installation where it is going to install, which partitions on which drive.
ronlau9 explained why you were unable to boot after removing the SD card. Did you try booting with the SD card still plugged in? You could probably have saved your data if you had used your xp CD to repair the xp bootloader and put it in the mbr. Not enough information for anyone to know what happened.