When ever I have partitioned a drive, I've always ended up regretting it. Each time I've tried to envisage the appropriate size for each partition, and I've always been wrong! This means I've then had to use something like Partition Magic to resize the inappropriate partitions, and on one occasion this totally crashed my system.
Maybe it's my ignorance speaking, but nowadays I always avoid partitioning.
Are you going to install your old drive as a slave and use it for backups?