Disk Wipe is a free portable Windows only data wiper to securely remove data from memory storage devices like USB thumbdrives, external hard drives and hard disk partitions. It supports any device formatted with NTFS or FAT, including MP3 players and digital cameras with an internal memory formatted by one of the supported file systems.
Erasing patterns include a one pass wiping with zeroes or random data, Russian GOST P50739-95 (2 passes), British HMG IS5 (3 passes), US DoD 5220.22-M(E) (3 passes), US DoD 5220.22(ECE) (7 passes) and Peter Guttman (35 passes). Its settings comprise volume label naming and thread priority to set up the amount of CPU power you wish to allocate to the data wiping process. There is an online help manual with screenshots but you are not likely to need it.
The best feature of Disk Wipe is that it comes with an integrated Hex viewer, this should be standard in all file wipers in my humble opinion, an Hex viewer allows you to see by yourself the hard drive surface to make sure that data has been effectively removed with nothing left behind. During inspection you should only see random characters or zeroes depending on the chosen wiping algorithm, anyone intending to use an Hex editor to check for data remanence will be better off selecting a pattern that writes zeros during the last wiping pass.
Disk Wipe is open source, it can be freely distributed and modified under the terms of the GPL3 license. The program is a small 965Kb download, a good tool to securely erase memory cards and partitions for free.