its a custom build there isnt any specific warranty.
It is a question of whether you believe the retailer will put the PC right if they know that you have been tinkering!
It is not uncommon for internal components or connections to come free when a PC is being transported, the quality of the packaging (or lack of it) and how the machine was handled on route are to blame most of the time when things don`t work when they arrive.
The following checks require the computer case to be opened so take the following safety precautions 1st, disconnect the power cord from the wall and take anti static precautions before touching anything inside, you can do this by touching a bare metal part of the case.
Check that all connections from the PSU to the MB and other components are connected securely.
Remove and reseat the add on video card securely, do the same with your Ram stick/s.
Check the case for any stray screws or bared wires that may be causing a short.
When you are happy that everything is as it should be reassemble the system and see if it will boot up and if the disk drive will open and close, if the drive doesn`t open it may just be sticky so gently open it manually with a paper clip, step by step guide @ http://pcsupport.abo...ht/ppdropen.htm
Good luck with it and let us know how it goes or if you have any questions.