The instructions directed me to download cloning software from the Transcend site. The instructions said to 1. install my new disk and hook up to a free sata port. 2. Run the software. 3. Detach the old disk and reboot.
This was misleading and didn't work--and I have a straightforward Windows installation. The problem is Transcend ignored the 'system reserved partition' which contains some of the boot code. The system reserved partition is a standard part of a windows installation. So I did not have a bootable system after cloning.
Even worse, the a Windows rescue disk couldn't figure out what to do.
finally I solved the problem by running TestDisk, a Linux utility, and created a new generic MBR. Now my system boots.
And even more finally I compared read/write specs for other drives and this one is inferior.... so pick another major manufacturer and do you research at some benchmarking sites. So minus another star for being slow.