Windows XP won't start?

Symptoms: When you start your computer, you get the black screen with a menu that tells you to start in safe mode, normal mode, etc. When you make a choice, you end up in the same place.

Solution: If you have Windows XP, you'll need an installation disk. Doesn't matter if it's yours or not. You just need a Windows XP disk. Any flavor. Put it in the CD drive and start your computer. Be sure the computer boots from the CD.
You will see the Windows installation message and the first question you will be asked is if you wish to repair Windows or install it. Choose "r" for repair. You will now be presented with a black screen that asks you which version of Windows do you wish to repair. Choose the one that is probably the first on the list--it should just say Windows. It may appear like this: C:\Windows.
You may get a second screen asking for the password. This is the password for the Administrator account. If there is not a password on this account, just hit "enter."
When you get to the C:\> prompt, type CHKDSK /P and let it run. It will most likely find errors and fix them. Once it's finished, Windows should start normally.

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Symptom: You've tried the primary fix (the easy one) and you aren't successful. You keep ending up on the menu screen and nothing works.

Solution: Once again, boot to a Windows installation CD. This time, though, you will need a CD that has the same version of Windows that you are running (for instance, XP Home, XP Pro). When you get to the first question asking if you would like to repair Windows or install it, choose the "install" option.
You will be asked to press the F8 key to accept the terms and conditions. Do that.
The next screen "should" ask you if you wish to repair an existing installation or install a new one. Choose the "repair" option and follow the prompts. It will probably ask you to choose the installation to repair, so do that. There should only be one instance of "Windows" to repair. Now you'll see it deleting files and installing new ones. The nice thing about this option is you won't be losing data. If all goes well, your computer will work just like before with all your programs and data intact.
One thing you will need, though, is the Windows Certificate of Authenticity--that is the five groups of 5 letters and numbers that should be stuck on the outside of your computer case.
If this doesn't work, you will probably have to do a full reinstalllation of Windows or repair the registry

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So--you've tried everything else and you still can't get XP up and running? Time to do a system reinstall.

If you have a recovery disk (or set) provided by the manufacturer or if you remembered to make one when you got the computer, put the first disk in the CD/DVD drive, boot from it, and then follow the prompts. The program will most likely format the hard drive and restore your computer to its original (factory) condition. Bad for you if you have not backed up your data.

When I have the opportunity, I would much rather use a Windows disk (same flavor of Windows on your machine) to install a fresh copy of the operating system. You would boot from this disk in the same manner as I described in the first two tips. This time, though, you will not choose "repair" but will proceed with the installation of a fresh copy of Windows. When prompted, I would recommend leaving the file system intact (that is, not reformat the hard drive) if you have data that you really don't want to lose. In the end, you will have two installations of Windows that you will be able to see in Windows Explorer, but only one will be functional. Your data will usually be intact. You will have to reinstall all your programs, though. All the files will be there, but no programs will work until you reinstall them.