When I paste an image (mostly schreenshot) into Windows Live Messenger to send it over, the image is compressed so much, that details can not be seen, event.
Is it possible to diable this "feature"?
It appears that Live Messenger isn't designed for this use case. While it's faster to paste the screenshot right into Messenger, it might be better to use a tool that fits better with the task you're trying to accomplish. You could use a shared drive, SharePoint, or you could use a screen capture program to automate some of the tasks associated with moving it, like creating an auto-named .png that you could then drag into Messenger.
If you're using Windows 7, you can use the Snipping Tool, which acts as a lightweight screen capture tool, with some great features like grabbing freehand selections and saving to a file.
I'm sorry I couldn't find a work-around that is as simple as your previous workflow. I hope this helps!