Repair to smashed screen, iphone still not working

[GT1978]

I have repaired my friends iphone 3gs screen after an accident smashing the old one, i believe that this was successful but the phone still will not power up or show any sign of life. I have checked on-line and still unable to find out clearly why this isn't working, is it a simple fix or would you say it is unfixable and better saving his pennies up for a replacement phone.

 

[Milla000]

I have had the excat same problem but it has happened to my phone from someone else, does the phone get stuck on the apple logo?