SATA 2.5 in 3.5 external enclosure?

Hi all,

I have an external "NextStar 3" 3.5 SATA enclosure and it works great with a 3.5 SATA drive.

However, I have tried two different 2.5 SATA drives in this enclosure and neither one was recognized (although both 2.5 SATA drives spun up). Both 2.5 SATA drives plugged in just fine, both 2.5 SATA drives have windows XP on them, both 2.5 SATA drives were pulled from working laptops and work great.

Is there some jumper needed on the 2.5 SATA drives? Is it because the 2.5 SATA drives are loaded with XP? Is there something inherently incompatible between 3.5 SATA and 2.5 SATA even though they fit the same connector? I've read that others have run their 2.5 SATA drives in their 3.5 SATA enclosures, so what's wrong?

What I want to do is clone an old 2.5 SATA drive to a new 2.5 SATA drive (I have not bought the new 2.5 SATA drive yet). The way I was planning on cloning was to put the old 2.5 SATA drive in a laptop, put the new 2.5 SATA drive in the external 3.5 SATA "NextStar 3" enclosure, then use "Acronis Clone Disk".

Yep it's weird! And yet neither of the two 2.5 SATA HD's read in the 3.5 SATA enclosure! Everything looks like it should work and AFAICT there is nothing wrong with the 3.5 enclosure, 2.5 HD's, 3.5 HD, cabling, power supplies, etc.

Thanks a bunch!