If you are found to be eligible to take part in this study, you will be randomly assigned (as in the toss of a coin) to 1 of 2 groups. You will have an equal chance of being assigned to each group. Group 1 will receive 90Y Zevalin along with rituximab and BEAM therapy. Group 2 will receive rituximab and BEAM therapy. You and the study staff will know which group you are in.