Temporary files do not automatically delete themselves. Something has to come along and clear them out, which would be the duty of the program that created them in the first place. Given this is from an old hard drive, there's nothing on your new drive (more specifically, your current installation) that's aware of making any temporary files at that location, and hence they just sit there.
You might be able to run Disk Cleanup and it would identify temporary files based on file extension (such as .tmp), but even then, there's no guarantee it'll find every temp file.