Try ACDSee Pro 2 - I like it. Take a screenshot, open it with this program, and change the resolution to JPEG through the File-Save As menu (it offers a series of formats in which you can save).
Then, go to the website http://pixs.ru and upload the image in JPEG format. It will offer you several link options. I like this one the most: Preview for forums - enlargement on click. Copy the link and paste it into the forum.
It's easier to convert the image to JPEG online in Photoshop and choose the quality so that it weighs approximately 490-530 KB, and then you can easily upload it to the forum.
