One of the frustrations of the S2 is that all the various android versions behave in different ways. My heartfelt thanks to Jan who posted a comment detailing a method for the 4.1.2 version. I have cut and pasted the comment below to help others find it a little easier.
Hi! I have been up all night but I HAVE FOUND A WAY to copy photos from S2 to pc. (I found your blog & instructions, but it didn’t work) I have 4.1.2 on my S2
connect phone to pc via usb cable (as though you are charging)
pull down the roller blind thing at the top of the screen
tap on the trident charging icon
hey presto! usb pc connection comes up!
it will be ticked on media device (MTP), so tick camera (PTP)
menu comes up on pc, choose photos via windows live
you can transfer all of them or select which ones you want.
I did this a second time after taking another photo with the phone, and you choose all the photos again OR just the new ones!!
But remember to retick media device before you disconnect (just unplug cable) OR it will not work as a media device