Well it seems fraps records avi files in a wierd format that is often not recognised by video players and editors.
There's a discussion about it on the fraps forum here
http://frapsforum.com/threads/fix-dark-f...ideos.758/
and some sort of guide to fixing it here
http://peter.corrosivetruths.org/2011/09...-too-dark/
I'll let you know how I get on
If you want to avoid the above fixes.
I used a video effect in vegas called levels. Using the prest "computer RGB to studio RGB" It sort of fix the darkness problem in my videos but I think it was just stretching the colour output values.
Okedoke I did a little homework on this subject.
You
can re-encode fraps avi files into more standard versions however here's the way I'm going to do it.
Fraps files seem to use the full range of colour values from 0-255.
However Vegas treats the value for black as 16 so the zero value for black in your fraps file won't be seen and higher values will look darker. You can check values by going into, view>videoscopes and then select histogram. You can see that your fraps file with have values at zero whereas most other video files will show values beginning at 16.
To Shift your fraps file values towards 16 you can use what I mentioned above with the "levels" video effect selecting the preset named "computer RGB to studio RGB".
I think this may not be a completely perfect fix as you are just shifting values rather than allowing the original to be used. On comparison it looks fine to me so give it a try.