The VG Resource

I took 150 screenshots as I played through Retro Game Challenge. I wanted a record of the sprites, particularly those from Guadia Quest and Haggleman, but I never planned on ripping them.

If you're interested in doing so or even just seeing the screen shots here's the album: http://imgur.com/a/XLAOs#0

I played the game in full screen, but the aspect ratio was correct.

It'd be very hard to get these into the correct size, as the aspect ratio wouldn't be "400%" it could potentially be "421%" - it'll be really hard to determine the exact level of increase these screens have gone through.

Instead of ripping from screenshots or gameplay footage, it would probably be a better bet to look into decompiling the graphics from the installed files.
These files should be somewhere in your steamapps directory (if this is a game on Steam, which I'm sure it is.)

But before attempting this, you should make a copy of them into a separate folder, so you don't risk corrupting any of the data necessary to run the game.