Windows reboots when certain booting files are not able to be located by the system. This usually is caused by either system files corruption or malware, virus,etc. It could be that the hard disk is experiencing problem of bad sectors. There are other things that can make a system to reboot, like when a windows is not fully installed in your system. Whatever the case may be there are always solutions to get your system working again. One thing is for sure that even the worse case scenario there is still some hope. It may have happened during some installation of important packages in your system, like anti-virus software, or other useful packages you deemed good for your system daily activities or during debugging of errors.
Step 1: Get to the Safe Mode of your system by depressing F8 during booting. It's the first screen you see when putting on your computer. After depressing F8 there will be some list of items. Move your cursor(the arrow icon) to Safe mode( which is the first on the list of items in windows XP) by using the arrow keys. Note that mouse doesn't work in this environment.
Step 2: Wait for the system to take you to the Safe mode environment. It's like your normal Windows XP screen only that it's a bit dull with inscription at the top and below the screen. In this environment you are not giving a full right to the system operation. If you couldn't get to the Safe mode environment for some reason you would have to use a recovery disk to repair the operating system.
Step 3: If you have any important files or folders kindly save them to a USB memory stick or any removable device or extra partition on your hard disk. You are advised to do so for safety of your important files, should in case of any total failure during debugging of the error.
Step 4: Network doesn't working or just missing from the scheme environment because it is not the option for network chosen. Try to run your anti-virus package to get rid of viruses If this doesn't find any thing then it must be a corrupt files problem or other factors.
Step 5: Put off your system and insert you windows XP installation CD and do your installation. In this case that's the best quick way out of it.
Step 6: After Windows installation you can now save your file on the USB memory stick back to your system.
Note: During booting the system will usually reboot after displaying quick information about the bug at the blue screen of death.The error is usually like this BIOS deactivated... STOP: 0x0000007E (0xC0000005, 0x805A82AE, 0xBAD13694, 0xBAD13390), etc.