Where can I find or purchase an operating system disk for my Dell Inspiron 6000 Model PP12L laptop?
If you're registered with Dell as the owner, and you live in the US, you can request replacement disks here - elsewhere, call your local Dell Tech Support line:
Otherwise, you're pretty much on your own. There should be a COA sticker on the laptop telling you what version of Windows the laptop is licensed for (XP Home, XP Pro, etc.) - what you want is a Dell Operating System Reinstallation CD with the same version (the disks are not model-specific). I've seen them for sale on Amazon. Worst case, though, you need to buy a copy of Windows.