How to quickly and effectively wipe a Win7 x64 hard drive

I have a Windows 7 Enterprise x64 system and need to wipe the 1.5TB hard disk drive quickly and effectively. Quick, I guess, is a relative term; so more quickly than I've seen with some wipe utilities (which can take a day). The HDD has only about 400GB of data on it.

I'd also like to wipe some specific folders on the network and on an external hard drive. What free tool do you recommend? Your help is much appreciated. Thanks.

Most people I know use DBAN or "Darik's Boot and Nuke". Its a selfcontained bootable utility that allows for wiping Hard Drives. Unfortunately the realities of the technology means you will need to wait a while - DBAN allows you to select how you wipe the drives (how many times and what pattern), a single pass 0 wipe which is enough for 99% of everyone (recoverable only with very expensive technology) will take a little over 4 hours. Even fast hard drives have a sustainable write rate of ~ 100MB/s which means that a 1.5TB will take that long.

DBAN allows for more exotic wiping patterns, like a seven run random pattern which will take almost a day at these transfer rates. Booting into a linux live-cd and running

dd if=/dev/zero of=/dev/sda 

would accomplish the same thing as single-pass 0-wipe

Doing a simple format on the Hard Drive will clear the Partition table and takes several seconds, However the DATA is still intact and recoverable easily using standard tools.

If you just want to clear the hardrive so you can reinstall the system a simple format will work fine. If you want to make sure the DATA is "destroyed" a single wipe through is your best bet.

As for clearing specific folders your best bet would be to overwrite the files with random data. Simply deleting the files will free their blocks on the filesystem but not wipe the data. Simple unix utilities like dd will let you overwrite files so they are unrecoverable.

If its a individual folder on a local drive you can use sdelete on windows, or shred from linux. For the whole drive use dban, 1 pass, and fill it with zeros - modern drives don't need the full guttman erase.

Network is trickier - the file systems are abstracted, and you can't be sure if its wiped, short of filling the entire remote file system's free space and deleting it after deleting the folders in question. There's no way to be certain you've done the deed.

How quickly you can wipe a drive depends on how secure you want it to be - just writing a few megabytes of random data over the partition table with dd will cause the drive to appear unformatted to the OS. However, in this case the data is still on the drive, and can be recovered with the appropriate software.

If you want the data to be unreadable, you'll have to write over the entire drive with random data, which could take quite a long time. Even then nothing is guaranteed - someone with a lot of money and/or an electron microscope could potentially read data from the disk.

The same procedures can be followed for an external drive, but there is probably no way to securely delete data from a network volume.