I would like to make my computer like a new computer, (re'build)

I have an XP professional operating system, and I also have the disk. Maybe just reinstalling the operating system will make it as a brand new computer? Vanilla copy

Can anybody out there help me? Or direct me to the right people?

Thank you in advance

Just pop in the XP disk and reboot your computer.
If the boot order is changed by default you will need to open your bios and change it to boot from the CD drive. Open the bios by repeatedly tapping f2 (sometimes f12 or even a different f#).

Be sure to save anything you want to keep to disks or a flash drive before you begin.

Once completed you should defragment your computer as well :)

I am trying to reinstall my OS to a fresh brand new OS so I changed the bios to cd rom should boot the first than I insert the cd and it start running and this error showed up "stop: c0000221 unknown hard error \systemroot\system32\ntdll.dll"
can any one help resolve this issue here please,
I was thinking if it’s the CD problem than maybe I can somehow download a new OS from the Internet and copy them to a CD and than reinstall, how about that? From where can I download an OS?

Thank you

You should remove non essential devices such as printers when reinstalling the operating system.

Keyboard, mouse, monitor, power cable only.

What does your CD actually say on it?

...maybe I can somehow download a new OS from the Internet...
It may be possible to download a dodgy OEM XP iso from illegal torrent sites. Whilst I would personally say this is morally acceptable if you have a genuine OEM XP license code stuck to your case, I think the moderators would still frown on further guidence provided on this area. Your license code wont work in the XP corporate versions that are usually more prevalent on download sites.