Is there a WIKI about how to copy and paste a (smaller) section of the Print Screen function from the clipboard into a Forum post?
You can't past pictures into a forum post you have to attach a .jpg or .png using the paper clip. I suggest using Jing as a free and easy way to take screen-grabs for the forum.
Another option is to paste the entire screen captured by Print Screen in to MS Paint, then crop it to the rectangle you want, and save it as a .png or .jpg file. Then you can attach it to your forum post by clicking the paperclip icon and then clicking Browse to find the file on your hard disk. Jing is a quicker way to save a selected area of the screen to an image file, but I think it won't capture things like menus that are dropped down. (I can't remember; I don't have it installed on this computer; it was on the one that died, so I've been using the Print Screen method for now).
but I think it won't capture things like menus that are dropped down. (I can't remember; I don't have it installed on this computer;
It can if you assign a hotkey to initiate a screen capture in the settings.