Cleaning up a PC before donating it to charity

The main reason I switched to Macintosh was to eliminate the wasted time spent caring for and feeding my Windows PCs at home. I'm in the process of ridding our house of a 3 year old Dell desktop in an effort to organize things and plan to donate the PC to charity. However there are a number of things that I need to do before dropping off the PC to the non-profit that redistributes old computers to charities:

1. Backup and remove any files or data that you want to keep. In this case I believe that I have all the files I need but I burned 3 CDs full of data just to be safe.
2. Time to wipe the hard drive completely - in my case while I have legal software licenses that will effectively disappear with my computer I wanted to take extra precautions by entirely erasing and overwriting the data on my hard drive too ensure that personal data was completed removed from the PC. In this case I went to SourceForge and downloaded a copy of Darik's Boot and Nuke'em (DBAN) there are copies for various operating systems (e.g., Windows, Mac PowerPC) and media formats (e.g., bootable CD, bootable USB and floppy drive).
3. Once you've checked and confirmed that the machine is clean of all data - pack it up and off to charity it goes.