remove the cdrom, connect the 20gb as slave, partition and format it, copy all data from 4gb to 20gb, remove 4gb, put 20gb as master in it's place and put back cdrom as slave. you can install 3.9 later, after that you will have back up the boot partition for safe reasons. make one or two spare partitions on new disk for temporary back ups. :-)
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for me it's better to install the new disk with sfs and not ffs from the scratch
sfsit's safer and can handle easyer big partitions.think about it
keep the old disk for backup reasons too!
