Having problems at startup.

Hi guys. Im new here and im not really sure about your policies.. but I searched through the forum pretty quickly trying to find a similar topic and couldn't find it.

Anyway. I'm not even sure this is the right category.. but somehow I would think it might be. Feel free to move it to something more suitable.

I recently bought myself a new setup and put it together a few days ago. Everything seems to work fine.. or, if you put this little problem aside.
Every now and then the computer (like.. i would say, every fifth-sixth startup) will reboot itself when loggin in to windows (when going from the loading screen of Windows XP to the desktop. OR if u happen to have a password it will happen just after u typed that one in and pressed enter). Now, I have no idea what this is about. I don't know if this is useful information, but I have the Intel X25-M SSD as my systemdisc and right now it's put into channel 1 master. First I had it in the channel 2 with the other storage-drive in channel 1, but changed that once I noticed it. There's a channel 0 too, would it be worth trying that one too or is that just not relevant at all?

What I also should say is that I first installed the XP 64bit, and when that one logged into windows there was a bluescreen right before the reboot. That do not happen in 32bit, it just goes dark and reboots.

Also. It has happen two times (so very rare) that the computer just reboots while being in windows surfing around and doing normal stuff.

So, is here anyone who might know that this is about/could give me some hint or anything?

Really appreciate any help.

Re Olof