need help with a regex expression to get youtube video id

I've got this URL for example

www.youtube.com/watch?v=NXtp7y24SHk&feature=g-all-u&context=G2dcd8bbF

I need help selecting the bolded part above and remove the rest.
I've got this code right now:

URL.replace(/(?:http:\/\/)?(?:www\.)?(?:youtube\.com|youtu\.be)(?:.*v=)(.+)\s/g, '<iframe width="360" height="250" src="http://www.youtube.com/embed/$1" frameborder="0" allowfullscreen></iframe>');

The problem is, it replaces everything before
NXtp7y24SHk&feature=g-all-u&context=G2dcd8bbF
and stops when it sees a space.
but how can i make it remove "&feature=g-all-u&context=G2dcd8bbF" as well

thanks.

1. It's easier to match the bit you want than to remove the bits you don't want.
2. What language are you using?

This will match the bold text in numerous regex flavors:

But as requinix was asking, what flavor / language are you using?