Hey i need help with my 350z i took the head unit out to put a new one in but the wires all cam out of the harness so i solderd them in to the new and realised my car will not start just keeps turning over and over again and the windows and also the lock button on my remote now dont work i have takin the new one out and now have none but why wont my car start

 

Check the fuses...

 

Ive done that and replaced 2 blown onesso now there all good but still the same deal

 

it's not really something that can be diagnosed over the internet
You're going to have to go over the electrical with a fine tooth comb or get help from an auto electrician

With the windows and remote not working you may have blown the body controller