Taking out the trash~

I'm trying to clean out my photo images. I bought a new/refurbished 27" Mac 2.8 Quad desktop and I plugged my cell phone into it to recharge it and I accidentally let it suck up all the photos from my cell phone which were a LOT! I deleted a lot of them but there's a lot that won't empty from my trash bin. The message I get is "The operation can’t be completed because the item “ ####” is in use." (I inserted ### just for this post).
I do know there's some photos being used in Picasa Photo albums but theres dozens I have no clue where they're being used. I don't see them in my iPhoto anywhere or Photo Booth..etc etc or my regular Picasa App. A lot of the photos that are in my Picasa Photo albums aren't photos I resized or turned clockwise.counter clockwise and such...and would like to delete those...but can't find them anywhere and this Mac is only a month old.
Is there any way to find out where I can find the photos and stop them out of being "used" as the message I keep getting from my trash bin keeps saying?
Thanks mucho
andy

 

Thanks Duke and John...
Coincidently thats what I did. I logged out and when I logged back in the a.m I was able to delete those items.

It was mostly all Sarah Palin's fault...LOL...I'm not kidding...I had a really funny photo of her in my photo album and I could not get rid of her. I wasn't even using it and couldn't find it in any of my applications...but that one friggin Palin photo held the whole thing up. I always knew she was trouble...LOL
Thanks mates