Windows Restart on its own!

Hi!

I have Windows XP SP3 and it restarts on its own randomly regardless of what I'm doing. I have the ASUS P5Q3 Motherboard, Intell Core 2 Quad Q9550 CPU, ASUS Nvidia PCX 9500 GT Graphic card, 2x2GB DDR3 1333MHz Kingston RAM, Seagate 500 GB 7200.12 Hard Drive, Samsung SH223 DVDRW and 600 Watt Super Silent Power Supply. I also have a sound card (Creative Soundblaster) from the previous system I had and a modem (PCI Modem with smart SP).

All this I bought a month ago since my last motherboard broke down. When I brought it home it worked ok for a day or two. Then it started freezing. The screen froze and I could do nothing but reset. After many atempts of reinstalling Windows - and it did froze in the installation process as well - I took it where I bought it from. They changed everything within the warranty and gave it back to me. I came home and then it started rebooting without any message. And when the windows start, it doesn't display a message that windows didn't terminate correctly. I took it again for service. I left it there for a day and they said it didn't happen to them. They told me to unplug the UPS I have. I took the box back, did as I was told and still it restarts on its own. I called them and they say it must be something I have connected. The modem router (Sagem) didn't display any problem of this kind with my previous system. And I did use a different mouse and disconnected the keyboard. I also have an external hard drive but this happens regardless if it's connected or not.

If anyone can help I would appreciate it greatly!

Thanks in advance!

Christos

Let me understand...you bought a system...that has not worked properly since you acquired it?

Or...did you buy all these indivdidual components and install them?

Either way...based on what you have provided thus far, it sounds like a hardware problem. What piece of hardware, I cannot say.

Full text of any error messages onscreen, please.

Louis

Hi!

My computer broke down. I kept the box, the sound card and the modem card. I bought all the rest. Yes, from the beginning there were problems. I took them back at the shop and they put in and installed new ones - at least they say they did. Now they told me it may be my router that's causing this. I don't think it's right but since I don't know much I can't argue. I'll try with a new router and at the same time I try to get help from here. If neither works I'll take it back and ask them to change it again. I don't know what else to do. It's been a month in this situation and it's very frustrating...

Thank you for your answer.