I just recently started using my copmuter to stream videos through my 360. Is there any way I can tell if the program im using is outputting the image as 16x9? I think it may be cutting some of the picture off. thanks.

Even if the program and XBox 360 are sending the entire image, your TV may lose some of it, due to overscan. All TVs overscan; some let you adjust/defeat it. What kind of set are you using?

ok i just did my own kinda test with a music video and it is cutting off a good portion of the picture on each side. Is there any way to fix this?

um its a couple year old high def sony projection set

the program im using allows me to adjust the resolution. currently i have it set to 720p seeing as how that is my tvs native resolution. Would lowering it a bit make any difference?

Adjustment through software:
Which software?
Maybe (but may unnecessarily reduce image quality).

Which model Sony?
How is it connected?

More generally, tThe are a couple of threads on the HTPC forum here which are good resources. See, for example:
http://www.avsforum.com/avs-vb/showthread.php?t=523614
http://www.avsforum.com/avs-vb/showthread.php?t=206854

Also, search forum for your TV's model line, e.g., the KDF-ExxA10.

Since you're using a 360--I lost sight of that--you might find something in the HTPC gaming forum, too. (If the problem actually lies between the Xbox and the TV, that's all I can say.)