How to completely remove datas of previous os ?

[securityguard]

Hello friends
I had windows 7 os but just few days back I have formatted my laptop all drives, but i am not sure that all the data are completely removed or not. And if not I want to...

Can any one suggest me....
my new specifications:
windows 7 ultimate
64 bit

 

[spirit]

When you install Windows and format the drive all data will be removed but might still be recoverable. If you're uncertain you can format your drive with this http://www.dban.org/ but personally I never bother.

 

[Agent Smith]

Burn DBAN to CD using IMGburn and boot the disk on the computer who's drive you want wiped.

http://lifehacker.com/5991848/how-to-boot-from-a-cd-or-usb-drive-on-any-pc

http://www.imgburn.com/

 

[beers]

I'd use DBAN or something if you wanted to sell the PC.

If you're just installing Windows fresh again, if you kill the existing partition from within the Windows installer it will dump everything from the file table on the drive. Then any new data will overwrite the existing bits, but your new OS will have zero reference of anything on the drive.