Question Wipe PC of personal data without reinstalling Windows?

[Mancolt]

I upgraded to a new laptop, and want to sell my old one to help offset some of the cost of the new one. I've been using the laptop for some time, so there's obviously a lot of my information embedded throughout Windows. I don't want to uninstall Windows and go through a whole new clean install process if it can be avoided (and I'm not sure doing that alone totally wipes the data anyways), but I want to clear my personal information such that it would be very difficult for the new owner to find anything unless they were extremely good and/or had very specialized drive recovery tools.

When I've disposed of old PCs in the past and not been concerned about keeping Windows, I've used some downloadable software that overwrites every sector of the drive multiple times. But in this instance, I want to be able to sell the laptop with Windows 7 pre-installed, as that will have a large impact on the value.

What's the quickest, safest way to accomplish this? If your recommendation includes something that would require reinstallation or revalidation of Windows, is my best bet just to download one of the applications that finds your Windows 7 product key and then record it for later use when reinstalling Windows? I'll probably also need to download an .iso of Windows 7 and put it on a flash drive because I don't have a recovery CD or anything like that.

 

[little_me]

Possibly easiest steps to do it with some "security"
Create new login
log in using new login
delete old login (from control panel)
make sure c:\users\oldlogin folder is gone
delete all other things you can think of
run disk-clean-up (windows tool)
empty recycle bin
get Ccleaner (or any other application with option to rewrite data on disks)
tools -> drive wiper -> empty space
select how many times, select disk to do it on, empty space should now be really empty. (bear in mind this will take HOURS even on 3 times setting)

Reasoning is that all old stuff linked to you would be deleted and marked as free space, which can still be read and restored since only start of files is marked as "empty" rest of data remains as is until overwritten. Once you overwrite said free space for real a few times, normal undelete/restore means wont work as well anymore.