Cleaned Dust from MacBook Pro and now it won't turn on

I have been given a 2008 Macbook Pro and there was a slight vibration coming from the right hand side where the hard drive is. As it was second hand I opened the back and removed all the dust, quite carefully with a small brush and a can of air duster. Now it won't turn on at all. When I push the power button a small hyphen of light appears at the front coupled with a slight clicking noise. That is all.

 

I'm afraid there's no chime sound, just the slight click when I press the power button.

 

I did not use a wire brush, I used a small soft artist paint brush. Naturally I double checked everything. I was just wondering if anyone had had a similar experience and whether there might be a simple solution before I take it to a repair shop.

 

SATA in place. I didn't remove anything other than the back cover. Careful as I was I am thinking something minute has been dislodged. Thanks all for your help, shall take it for repairs and report back in case what they find can help others in the future