Sorry, but I disagree with the comments on not using the X-clamp repair. That is the only way I repair Xboxes. I don't have a reflow station and don't plan on purchasing one. I imagine the cost to reflow the Xbox is more than my customers are willing to pay for their old console.
I always caution my customers that the RROD repair may only last a few weeks to a year or more. I give them a 60 day warranty against future RROD's. As old as the Xbox 360 is becoming, if a customer can get another year out of their console for $50, they are happy.
Using the right length screws and careful application has proven successful for me more times than it hasn't.