Some e-mail packages ask if you want to reduce image size for e-mailing, and there's one forum i'm on (not here) that shrinks photos if i try to attach them to a post and there's nothing you can do about it. I don't know about farcebook as i don't do it.
Don't think it's anything to do with the graphics card / screen on your laptop if they look OK in PSP
Also, PSP can be set to reduce size / resolution when it saves jpg files. There is a way of telling it not to do this, but it's a while since I've used PSP and can't remember how. It will be an 'option' setting somewhere.