Need some help with hard drive 'swapping'.

What I would do is hook *both* drives to your computer, with the 144 as the main one. Format and reinstall your OS of choice on the 144 one, keeping everything saved on the smaller drive and CDs/DVDs as needed, then transfer from the smaller drive to the larger. Then, remove the smaller drive and put it in your sister's computer, reformat, and install her OS of choice. This way each hard drive has been formatted and installed on the computer it's going to permanently live in, which will solve any driver problems Windows might have.

As a side note, its things like this (particulary the data juggling) that make me glad I use a second hard drive as a dedicated data drive, with my primary drive used primarily for the OS and software. That way, I can always swap out the primary drive or reformat it without juggling my data around. Quite a usefull technique if you can afford a second drive. Partitioning a single can help as well, at least allowing you to keep one section of the hard drive with your music/video/documents/etc intact while formatting the other.

Jam it back in, in the dark.