Windows 8 D-drive Problem, Tried Everything PLEASE HELP!!

Really hope someone can help with this, it's driving me INSANE. I've tried everything I can think of.

I've got Windows 8 consumer preview installed on my C-drive (240gb SSD). I also have a 2.5" Toshiba HDD (pulled out of an enclosure) set as my D-drive used just for storage (games, photos, videos and music files).

Both C and D drive are healthy and have been benchmarked and tested for errors so it must be a setting on the OS or something similar.

My C-drive has no problems whatsoever. D-drive however is suffering a problem, whenever I double click a folder e.g. a MP3 album nothing happens for about 4-6 seconds.... THEN it will open the folder after the 4-6 second delay. It's the same with everything on D-drive. When I'm downloading something to D-drive the drive becomes almost in-accessible because of a performance slowdown. I tried playing Skyrim whilst downloading a file and Skyrim was so choppy it was unplayable. Never had problems like with a hard drive before, I don't know what the problem is :s

Sometimes it's fine though, I booted up yesterday and my music folders were opening snappy like normal. It comes and goes irregularly, I can't see a pattern of slowdown it's completely random.

PLEASE HELP. IT'S DRIVING ME INSANE

Are your Power Options set to turn off your HDD (in Advanced Settings)? The delay could be the time it takes for the drive to spin up.

Hi James Clark;
I had a similar problem type of problem when on occasions the system went into slow motion.
Checking a gadget I had installed showed considerable cpu activity and constant disk activity. I opened task manager and no process appeared to be consuming the amount of cpu activity in use. Checked the tick box at the bottom to show processes from all users and it showed up as Windows Indexing service. i.e it found a new drive had been mounted and was indexing it for rapid searching. If the drive was dismounted and the system rebooted no go-slow. Finally I just let it get on with it and index a 3TB drive.
I am not saying this is the problem but it may be worth checking.
BesB