You can also pin from within Pinterest without a Pin button. Click on the + button next to your user name, go to Add from Website, paste in the url, click Find Images and select the image you want to pin. A bit of a faff but it can be done. HTH.
I know this is an old thread, but I just came across it while searching for how to add a PinIt button in Internet Explorer 10 on Windows 8. I really like about 90% of Windows 8, and I really like the app version of Internet Explorer 10, but this kind of thing disappoints me. I think the problem is that the "metro" version of IE10 (the one you access from the Start screen) disables all add ins, and therefore won't run extra bits of code like a PinIt button. I think this is a big mistake by Microsoft and I hope they will rectify it.
I didn't realise you could get Chrome as a metro app. Off to check that out right now!
I was not able to get it to work on Win 8 either using IE. But I installed the extension on Chrome and it works fine. So install Chrome (it is a metro app) and then install the "Pin it" extension, which puts a little button that allows you to pin from the internet in Win 8. HTH.
I'm a frustrated Pinterest addict. I cannot pin on my new laptop. Please tell me how to install the Pin it button. I have tried dragging the button. It says drag onto toolbar but as I don't know where that is on this new fangled machine I'm getting nowhere. Help me please!!!!!