Agree with Norm. Use either Mediainfo or the media properties window inside of Vegas. This one.

If indeed the frame size of your media is 800 x 600, there is little wonder that it looks pixelated when rendering at 1920 x 1080, especially given different aspect ratios. You can upscale, but it will look pretty terrible. The screen shot of your timeline is even more perplexing. There, your project frame size is 1600 x 900 at 128 bits which means that your project settings have been set to 32 bits rather than the usual 8 bits.
wwaag