Sounds like you used a demo version of another program and imported that media into Vegas. That means you need to purchase and register that other program in order for the X to disappear.

I am using Indeo as my codec and my file format is video for windows.

Also i have a trail version of vegas could that be the problem?

Register the product, or plugs that you are using, this will then go away.

Ooohhhh!! Ouych!!!! Indeo? Why on earth would you use that horrible, antiquated mess?
Register Vegas, use the Vegas or MS codec. You'll see great vid. No matter what, Indeo can't be made to look good.

I did not buy this so i cant register it can i if i am wrong how can i register it?

The demo of Vegas just puts a Vegas logo ever 30 frames or so in your video. It sounds like you're using a demo of a Boris program (Red, FX, or GL). If you DO NOT use those in your project, the x won't show up. How do I know? I have the Red demo installed and don't use it in my projects, so it doesn't show up. :)

i am using fraps to get the part of the demo i am using is that one?

Also how do i change the codecs?

oh and one more thing i dont know this program very well so if you could give me a step to step guide on how to change it that would be really helpfull thx much.