Motherboard problems

hi i am new in this forum this is my problem i buy a new case for my computer
it came with the power psu whe i took the motherboard out and i put it into the new case it did turn on but when it tried to go to windows the compu restart by it self and keep doing that so i put the windows xp cd in the tray
and when i try to install windows xp it start from the cd and start loading the
file for windows installation and a screen came aut telling me the i already have a windows installation in the disk so it give two options to continue press c so i did and the computer restar by it self someone can help me please

i have
p4 socket 478 2.53
p4vxasd2 motherboard
500 watts psu
80gb hd

Did you do anything else to the board when you changed cases? Make sure if you have any cards in a PCI or AGP slot that there in tight. Make sure all memory sticks are in tight. Make sure your not grounding the mainboard to the case in anyway.

in my old case the holes had this yellow screws where u put the mobo on top of them right then u tied the mobo with the regular screws the thing is that my new
case has the holes in right positon and i didn't put the yellow ones first and when i turn the computer on the fans came on the hd was spining but no display i took the motherboard out i put the yellows screws first the i turn on it did work but now my memory is f**** what did wrong

Now i have test my ddr memory with DocMemory Diagnostic and it says the my memory is good but when i start windows with that memory restart and keep doing that until i changed to other slots sdram an put 128 sdram
i don't thik the my memory is bad because i tested
and is good i think is the motherboard slots what do u gus think.
thanks

You may need to reinstall windows. What windows are you running?

i alredy try to reinstall windows but i couln't do it with the 512 ddr i had to use the 128 sdram the i have.