Moved computer to new case, now wont boot

Hello,
I have moved everything from one case to another, simply cause i needed the extra room for what iv been planning, but when i had moved everything, plugged it all back together, screwed everything in, it just wont boot, it will turn on, thats it, nothing else after, which is rather annoying since i could do with the processing power to watch videos in HD,and my netbook just doesnt cut it, but my spec are

foxconn rc4107 RS2H mobo
P4@3.2ghz
80gb PATA
250gb SATA
128mb ati x200 graphics card
some realtek crap
no idea what PSU it is, theres too many numbers an confuses me
XP MCE 2005 SP3

iv tried taking it apart, looking for screws, taking apart putting it back together, checked EVERY cable, an hell, even the fan cables PLEASE HELP