Help Desire Z - screen lines

[hatsumomo]

hi,

I droped my phone and now my screen doesn't work anymore but only after the boot. On boot I can see the HTC logo then there's lines on the CyanogenMod logo and on the home screen so I don't understand where the probleme comes from. Is it hardware or software ? Hope my exploinations are clear enough (it seems that's it's not possible to put images on this forum).
Thanks for your help.