Want Windows back...
If you have a valid license for Windows and know the Windows activation code or product ID, you can at any time legally use any Windows installation medium to re-install the Windows for that license. The installation should be recognized as valid by Microsoft upon activation, otherwise you can call in the activation code. A safe copy of XP might be hard to download, but XP is common enough to be found around as a DVD.
Here are Microsoft authorized installation DVDs for Windows 7. Note the "bootable" versions that make it easy.
https://sites.google.com/site/linuxl...ry/windows-iso
Using the original installation medium allows you to format the HDD with the number and size of partitions you want and makes it very easy to install linux as a dual-boot.
The Dell system number makes it easy to re-install all the drivers, and you can install or un-install Windows as you please. Windows, some people here don't like it, but sometimes, some need it.