Computer freezes at startup

Hi guys!
Few days ago my computer kept restarting when I was in any game or doing nothing, so I decided yo reinstall the OS. I burned a CD with Windows XP but every time does the same thing:
I boot-up the CD, I format the partitions, then the files are getting copied. After that, Windows reboots as usual, but then it freezes at loading screen and I don't know what to do :(.
I checked the coolers, the GPU, CPU, the RAMS and the HDD.
The other day I tried to install the os again, but after the loading screens it gaved me blue screen, every time a different error.
Today I tried again but now keeps freezing but no blue screens of DEATH.
I hope you can help me because I can't buy a new pc until Xmas.
My computer's specs:
AMD Sempron 3400+ with 1,5 gb of RAM, Asus K8V-VM (motherboard), ATI Radeon X550 (graphic's card) 160gb hdd ATA.
I even tried using Ubuntu, but he freezes at loading screen.
I hope you can help, and sorry for my bad english.
 
Okay, if that's what your caps look like, the best thing to do is to replace the motherboard
 
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