What would cause a computer to restart just before it gets to Windows XP start up and continue to restart and restart?

It is a program that restarts your computer. It sounds like you may have a corrupted program on your computer that is causing the problem. This happens for many reasons . It happens most often during reloading of programs and may have happened at the factory. No way of knowing for sure.

I would suggest doing a systems restore. This should be already on your computer.

If you do not know how, contact your ISP or computer manufacturer and hey will instruct you on what to do. Your computer should me under warrantee and while it is this service should be free.

ANSWER:

Let's ask a few questions before we can isolate the issue. First, how long have you owned your computer? (Is it new? Have you had it for a few years? Have you been doing your updates as they come in?) Second, did you add new hardware? (if you did, was it a communications device? IE: network card, wireless card, modem.) And further, did you use a PCI slot that wasn't the last in the chain? (The very bottom of the board, or close to the video card?) And lastly, did you install a new memory stick?

Now, let's address each of these things.

1. If the computer is new and you are having this continual re-boot issue, you should contact the manufacturer for support. If you had it for a while, go to the next step.

The most current updates that can, and have regularly, caused the issue you describe are the service updates, or "service packs" for Windows XP Pro or Home. (Mostly SP2) The registry and MBR (Master Boot Record) are not re activated correctly due to a bad downloaded .EXE) In this case, there is only one thing to do. You must remove or uninstall the service pack. Both, SP2 and SP3 have an uninstall program, and it can be performed through the "Add/Remove" tab in the "Control Panel" Since the computer won't boot beyond the initial biOS start-up, then you will need to keep your finger at the ready to hit F8 so you can enter "safe mode" (pressing the F8 key on your keyboard repeatedly during the biOS startup.) If you are successful, then navigate your way to the Control Panel and then to the Add/Remove tab. simply remove the service pack, and reboot the computer. The original condition should be achieved at this point, and you can try to let the Update site try again, or, you could just go to the Microsoft website and download the service pack manually. Because of the length of the instructions, go to: Microsoft.com/kb/875350">http://support.Microsoft.com/kb/875350 Here you will find the instructions to help you remove the SP in several different ways. (I recommend you go straight to the last one since you can't boot into Windows.)

1. Almost all mainboards now, have sound and network cards "built in" and are not required to have add on cards. Most of the new system architectures of today have a specific slot in which to install a communications device, should the need for additional or replacement cards to be installed. They are "Electronically Keyed" as are the new cards, so that the communications device can only work in the one "slot". (This has to do with the addition of the PCI-E bus in the newer systems.) In most systems, the location will be at the last slot on the board. (The furthest away from the CPU.) Some manufacturers have been gracious to color the slot "orange". Soon, it will become a standard, but until that day, currently, most manufactures enter this vital information in their manuals as a side note. Not fair to the most of us, but hey,,,it's their thing….for now! The result of installing the communications card in the wrong slot will yield the problem you have described. In some cases, the computer won't even start. (The board, power supply or both will detect a voltage variant and prevent the startup to prevent damage to the board and interface.)
2. And lastly, with the advent of DDR2 and the PCI-E boards, there are some issues with memory and the types being used. Some boards have color-coded memory slots. IE: if you have three or more memory slots, (4 is the most on most boards) 2 will be the same color, and the 1 or 2 if there are 4 will be a different color. This would indicate that a.) if you are running two "like" sticks of memory, they should be installed in the same colored slots, leaving the 1 or 2 slots empty. (Even if the board has a "blue-black-blue-black" you would only use the "blue-(empty)-blue-(empty) configuration.) b.) if you are using size different sticks, then the slots "color code" would be used. IE: if you have two sticks of 512mb and one stick of 256mb then the two 512's would occupy the "blue" slots, and the 256 would occupy the "black" slot(s) This also applies to the "FSB speed" (Front Side Bus) of the memory. Ideally, two sticks that are of a different speed, (yet the board supports both speeds) then you would segregate the speeds in the corresponding coded slots.

In summery, there are several things that could cause the issues you have described. Check each one, and see if any of the suggestions mentioned here, could be a resolution. At the last ends, take your computer to a qualified technician, and have them fix it for you.