this article may be helpfull
FORMATTING
While running your current version of XP , insert the XP CD in the drive. When the
setup menu appears, select "New Installation" (clean install) from the pull-down menu.
Also, select
"Advanced" and place checkmarks in the two boxes.
2. Next, your computer will start copying files and then reboot. At this point, select
the same drive/partition that Windows XP is currently installed on. Select the
option to "format" this partition using either FAT32 or NTFS.
3. After the drive/partition is formatted, XP will begin the setup process and install
"clean".
4. After registering and activating XP, be sure to run a "Defrag".
For details:
http://www.winsupersite.com/showcase/windowsxp_sg_clean.asp
Note: It is important to visit the web site of the manufacturer of your computer to
obtain any special XP drivers.