I have a laptop with a UK English version of Windows and a French keyboard (AZERTY...). I have been using the Google Pinyin IME for some time now but I can't figure out how to enter a "half comma" (顿号, dùnhào, i.e. this type of comma: 、). There are explanations for non-AZERTY keyboards (e.g. at LaoshiLink) but I haven't found any for French keyboards. (I did a web search in French but I wasn't lucky.)
Since I figured it out after some more searching and trying, here is the answer:
After starting Google Pinyin IME, right-click on the keyboard button (软键盘 ruǎnjiànpán: software keyboard). From the menu that appears, choose 标点符号 (biāodiǎn fúhào: punctuation marks). This will bring up a keyboard on the screen; the dun comma is on the top row, on the same key as the number 2. You can than enter the dun comma using either the software keyboard or your hardware keyboard. You can then close the software keyboard again by clicking on the keyboard button.
Unfortunately, I am not aware of keyboard shortcuts to do this.