I have a Dell Latitude with windows xp on it i would like to erase all the memory on it how do i do it ?

I see two ways to do this - if you want to format the hard drive and remove EVERYTHING - you can use CCleaner from Piriform.com to wipe the hard drive after starting it in XP and selecting the "wipe hard drive" under Tools. Change the default selection from "wipe unused space" to "wipe hard drive". It will have NOTHING on it when things finish. No operating system at all.

You could then install a free Linux distro on it and have a working computer without a Microsoft operating system.

CCleaner or another program similar to it *might* be able to remove all your personal information but it won't be a clean factory install, there might still be personal information in the registration and a couple of other places. I would NOT sell one that had only had the personal information removed that way - I might keep it as a "spare".

If you have a Windows 7 Upgrade disk and install it over XP, it will wipe your personal information and install a "clean" copy of Windows 7 over XP. You would need to update the drivers, possibly flash the BIOS to a more recent version (you don't mention which Dell Latitude model you have), and run Windows Update until the OS is current again. But personal information will be GONE.

If you are going to sell it, give it away, donate it, or turn it in for recycling - format the hard drive with CCleaner & select the maximum number of over-writes. Advertise it for sale as being formatted - no operating system. Or check eBay to see if anyone is selling a Dell Latitude operating system (OS) disk (#1 in the recovery disk set) that has Windows XP on it and use that to do a clean install.

You can download & install Driver Booster from Iobit.com to get the drivers quickly updated after a clean install of just the operating system, then run Windows Update to get the OS up to the current level. Windows XP support stops in about two months - so an upgrade of the OS to Vista, Windows 7, or any of the Linux distros (free or cheap with no activation code needed) would give you a working laptop - that will run faster as Linux is written more tightly to run faster on the same hardware.

But I don't know of a way to make sure that the operating system would still work after you removed ALL of your personal information.

You use the Windows XP recovery and install disc set that came with the computer and use them to reinstall XP putting it back to factory. The reason control panel and other basic things do not work is because XP has corrupt operating system files and needs to be reinstalled using the operating system install / recovery disc that came with the computer if you can not find them then try and order them from the computer manufacturer. Buy a new boxed install for Windows 7. But be sure and run the W7 compatibility advisor first. Support for Windows XP is ending in April according to Microsoft.