I second reddazz suggestion. Remember that if you are using a LiveCD to test your system, the performance will be much slower than it would if it was actually installed on your harddrive. It usually requires more RAM as well.
For example, Ubuntu and its "cousins" usually recommend 192 MB of RAM when installed. Running from the CD, they would most likely recommend twice that amount of RAM (could not find any source to back that up, but it usually is that way