Windows 7 External HHD not always recognized

[bimfi]

[FONT=&quot]I have been having an on-going issue for some time with my external WD My Book. There are times when it is not being recognized by Windows 7(pro). It has three interface options (fire wire, esata, and USB). I have tried all three at one time or another, finally settling on the eSATA interface. When it IS recognized, it runs smoothly, with no hiccups. But when I try to shut down the PC, sometimes it hangs up on the shut down screen for a long time (more than 15 minutes at times) until I actually press the on/off button on the My Book. When I do this, my PC immediately shuts down, but then, if I start up my PC, Windows does not see it again. I then have to power the My Book back on, then power up the PC and hope that it is recognized again. It’s not a big issue, because it is not frequently used, except for storing back-ups. It’s just something that is a nuisance. I’m not even sure that it is a Windows problem, because sometimes it is not detected in BIOS. Any suggestions as to why it is intermittently being detected and why it is hindering the shut-down process? [/FONT]