Effective way to wipe a laptop's HDD without erasing the OS?

[Ibsenfan]

So I have a laptop that I want to sell since I will be buying a new one soon. I want to try to sell it to a new owner, but I'm a bit paranoid about what info is left on the hard drive.

I want to wipe it clean, but I don't want to erase the OS as I don't have the cd to reinstall it. Is there an effective way to do this? There are a few options I had in mind but none seem ideal. I was thinking I could format it, fill up all the HDD space with non-sensitive data, then format it again, but that is time consuming and I don't even know if that would work. I was also thinking of just DBANing it and putting an unofficial copy of windows on there, but that too is not ideal as I don't wanna sell a laptop with non-legit stuff on it. Any help would be appreciated.

 

[drtweak]

download CCleaner. Delete and uninstall what you want or do a Factory Restore if you can (Will make it be like new) that is either though a DVD that came with your laptop or though a hidden partition and you have to hit a button at startup to start it. Otherwise Erase what you want and then download CCleaner. In the Tools Section there is a drive wiper. You can have it wipe free space and let it do a 3 Pass. This will erase any data that is still there but just removed from the windows index files.