(How to reinstall Windows 2000/XP without loosing your data)
Boot your computer with your Windows CD-ROM inserted. When you get the 'Press any key to boot from CD' message, do so. (If you don't see that message before Windows starts, restart Windows, press the key you're prompted to enter for your PC Setup program, and change the boot order so your CD drive is first.)
At the 'Welcome to Setup' screen, press Enter. The R (repair) option takes you to the Recovery Module, which is useful if Windows won't boot, but it's no help with a reinstallation. Soon you'll be told that there's already a Windows installation on the computer. Press r for a repair reinstall or Esc to begin a complete, destructive one. For a complete restore, select your C: partition and press Enter. When you get the warning that says an operating system is on that partition, press c. When you are asked your partition preference, select Leave the current file system intact (no changes). When you're told that a Windows folder (or Winnt folder for Windows 2000) already exists, press l ('ell') to delete it and create a new one. Follow the series of prompts. When the installation program asks for your name, enter temp.
Once the installation is complete, your system will reboot into Windows, and you'll be logged on as user Temp. If the screen is difficult to read, reinstall your graphics card driver.
If you're reinstalling Windows 2000, log off as Temp and back on as Administrator. Now log off and on again, this time as Temp. Open Windows Explorer and navigate to C:\Documents and Settings. One of the subfolders will be named Administrator. Another will be named something like Administrator.computername.
Select Start, Programs, Accessories, Command Prompt. Type cd "\documents and settings" and press Enter. Then type xcopy administrator\*.* administrator.computername /s /h /r /c, replacing computername with the last part of that folder's name (after "Administrator.") in Documents and Settings. Now press Enter, and when you're asked about overwriting files or folders, press A for All.
If you have any users on the old installation besides Administrator, continue with the "For Both Windows XP and 2000" section. Otherwise, open Windows Explorer and make sure your data files are where they belong. Then go to Control Panel's Users and Passwords applet and delete the user Temp before skipping to "Finishing the Job."
(For Both Windows XP and 2000)
Reopen Windows Explorer. Select your C: drive (you may have to click Show the contents of this folder). Right-click in the right pane and select New, Folder. Name the new folder oldstuff. In the left pane, choose the Documents and Settings folder. It should have subfolders for each user from the previous install, plus one for Temp and a few others. Move the folders for your previous user names to oldstuff.
Select Start, Control Panel, User Accounts (Start, Settings, Control Panel, Users and Passwords in Windows 2000). Create an account for each user who was registered before the reinstall. Be sure to use the exact names. They are the same names as the folders you just moved to oldstuff. In Windows XP, at least one user must have administrator privileges.
Log off and back on as each user, before logging back on as Temp. Make sure that you select Log Off and not Switch User at Windows XP's Log Off dialog box (this isn't an issue in Win 2000).
Log on as Temp, select Start, Programs, Accessories, Command Prompt (in XP, Start, All Programs, Accessories, Command Prompt), type xcopy c:\oldstuff\*.* "c:\documents and settings" /s /h /r /c, and press Enter. Press a when asked if you want to overwrite a file. Log off Temp and log on to each restored account to make sure everyone's documents and data are where they belong. Log on as an administrator and run Control Panel's User Accounts applet again to remove the user Temp.
(Finishing the Job
Now you've got Windows going, but not much else. You may have to reinstall your printer, sound card, and so on. Luckily, if a driver for the gadget came on your Windows or vendor restore CD, it was probably reinstalled automatically.
You'll have to reinstall your applications to reintroduce them to Windows. Some of their settings will not be changed by the reinstallation, but those that were stored in the Registry were wiped out.
Once your Internet connection is running again, browse to Windows Update and download all critical updates for your version. Then visit the sites of your hardware vendors to update your drivers.
After the reinstall, some of your data may not show up where it should. Search for it in both your Application Data and oldstuff folders, and see if you can move it to the folder in which Windows or your apps are looking for it. If you find a folder called Identities with two subfolders whose names are long and indecipherable, try moving the contents of one to the other and see if your data reappears.
You've probably guessed that the final step is deleting the c:\oldstuff folder--and the Administrator folder in Windows 2000. Make this the very last step, however. Wait a couple of days, weeks, or even months until you're confident that all of your needed files are accessible.