1. You ran pvcreate on the disk - /dev/hdb - not a partition (/dev/hdb1). If you want to create a partition to use with LVM, create one over the full disk (hdb) and set the type to 8e, Linux LVM. Or just create the pv using the full /dev/hdb disk.
2. Do you really want to wipe your hda1 and hda2 partitions clean by initializing them?
I suggest your read the LVM howto
. It's got all the information you need.