Windows must have written something to the drive. Or did you use a bootable disc for the diagnostic?
I just did something similar with the external for my Tivo HD, but I used the manufacturer's boot disc diagnostics(WD data lifeguard, DOS).
The 4 year old, 1 TB drive "passed" the test. Took almost 24 hours though(?). No issues on start up when reconnected.
You might double check the cable and connections. Sorry I can't offer more.
I just did something similar with the external for my Tivo HD, but I used the manufacturer's boot disc diagnostics(WD data lifeguard, DOS).
The 4 year old, 1 TB drive "passed" the test. Took almost 24 hours though(?). No issues on start up when reconnected.
You might double check the cable and connections. Sorry I can't offer more.