I notice there was a query about this some time back, but couldn't see a soloution.
This has happened on two computers of mine, both less than 3 months old.
I suspect a virus, but I can't see anything.
Any bright ideas, anyone, please. I'm stumped.

hi, there was actually a solution, but it all ended up in reinstalling windows, thats if it is the same problem. What happened with those pc's or laptops was that people ran them without a antivirus, or the antivirus was struck by a stronger virus or got disabled, but anyway in the meanwhile the harddrive got infested with viruses and covered everthing, the user of the pc then either re-enabled or installed another antivirus on and did a scan which found all these virus infected files which were corrupt and started to delete them. It even deletes windows files which are required for windows to start up, which in this case is the userinit.exe if i remember correctly (will search it up again now and give exact info and sites) and the only way to get it back on the harddrive or the easiest way was to use the windows setup and repair disk, then press r at the first screen which takes you into a CLI (command line interface) and there you have to make a new copy of the userinit.exe from the cd to the C:\WINDOWS\system32 directory.

Oh here is the other thread

Ok, so that is one possibility, is that the problem? If not then I am asuming that you are getting the BSOD (Blue screen of death) and that your computer is booting up and after trying to start windows it finds that there is a hardware failure and reboots and tries again... if THIS is your problem then tell me and i will post what you will need to do in that case. Oh and try to go into Safe Mode if you can (press F8 at startup and select Safe Mode and try "Last Known good configuration" aswell) and tell me what happens.

Best of luck

If you can get the pc to boot try the following
1.Navigate to the Control Panel in Windows XP by left-clicking on Start, followed by Settings and then choosing Control Panel.

2.In the Control Panel window, open System.

Note: In Microsoft Windows XP, depending on how your operating system is setup, you may not see the System icon. To correct this, click on the link on the left-hand side of the Control Panel window that says Switch to Classic View.

3.In the System Properties window, click on the Advanced tab.

4.Locate the Startup and Recovery area and click on the Settings button.

5.In the Startup and Recovery window, locate and uncheck the check box next to Automatically restart.

6.Click OK in the Startup and Recovery window.

7.Click OK in the System Properties window.

8.From now on, when a problem causes a BSOD or another major error that halts the system, the PC will not automatically reboot. Rebooting manually will be necessary.

Might not be your problem but worth a try!!