It could be the native resolution of the laptop that's unsupported by the monitor, but when it's in as VGA it just makes the best of it hence why it's fuzzy. Try cycling through resolution on the setting of the second monitor in Display Properties, see if it makes a difference. I'm not well versed on samsung monitors, but with Dell you can select the input or stick it on auto, and if it doesnt detect a signal it supports sometimes it wont bother switching to that input at all, so maybe select the DVI and cycle through, but again, it's basically converting an analog signal(VGA) to a digital input (DVI) so it may not work too well either way, and the monitor is still getting the same signal quality. Your best bet is to splash out and get a €20 HDMI - DVI cable, you'll get a better signal from that anyway. Or just try to mess around with the VGA input/output to get a better resolution.