In general, SATA-II controllers are backwards compatible with SATA 150 hard drives. This should be discussed in your motherboard manual. If you have doubts, check the motherboard manual or website before you purchase.
Using SATA-II hard drives on motherboards with SATA 150 motherboards is discussed in the documentation for the particular SATA-II hard drive.
Currently I have a Seagate 250GB SATA 1 on my DFI mobo which has SATA 1 connections. I plan on upgrading to an ASUS mobo with SATA 2 connections.
Now on to my question:
Can I put my SATA 1 hard drive on a mobo with SATA 2 connections?