Hi
Yes, your going to need the windows installation cd or recovery cd for the computer.
if you have the windows installation cd here is how to perform a repair install, all the files(pictures documents etc) will remain on the computer hard drive.
how to perform a repair installation
this is for xp, but its
similar on 2000 and on vista.
insert your Windows XP Setup CD, and restart your computer.
1.When
the Press any key to boot from CD message is displayed on your screen,
press a key to start your computer from the Windows XP CD.
if
not then the computer is not set to start up from a cd, you can either
enter the setup / bios to change that setting OR right when you power
up the computer look at the screen it will say what button to press in
order to enter boot menu or bios, it will very likely be button F12 or
similar, it should say on the screen when you power on.
if it
doesn't, then you need to go into the bios and change the boot order so that the computer starts from the CD first.
after that you should be able to start from the cd and install the OS (Operating system, eg.Windows)
here's some info on how to work the bios:
http://www.whitecanyon.com/how-to-change-boot-order.php (click the link to visit another page with instructions)
Repeat step 1 when you have changed the boot order.
2.Press ENTER when you see the message To setup Windows XP now, and then press ENTER displayed on the Welcome to Setup screen.
3.Do not choose the option to press R to use the Recovery Console.
4.In the Windows XP Licensing Agreement, press F8 to agree to the license agreement.
5.Make sure that your current installation of Windows XP is selected in the box, and then press R to repair Windows XP.
6.Follow the instructions on the screen to complete Setup.
7.Ones
windows is working you will need the drivers for your computer, they
are at the makers website,
hp and compaq.
www.hp.comacer
http://support.acer-euro.com/drivers/downloads.htmlDell
www.dell.com and so on.