Resizing ReiserFS

Hi everyone, Can I resize my / patition? I installed 8.2 to a large (100gb) drive and would like to reduce the / partion to something more manageable. I tried to resize with Yast/Partitioner, got a message advising me that resizing ReiserFS is possible, but has not been very well tested. I proceeded, but then got a message that this cannot be done on a mounted partition. Can I unmount a running / partition? Another option would be to run a dos/windows based partiting program to reduce the size, but I am unsure what effect this will have on the operation of 8.2. Thanks for any suggestions. Jim Flanagan