This is the number of times the privacy software application will overwrite a particular file on the hard drive. There are many Department of Defense Standards and non-governmental standards in what should be the optimum number of times for overwriting. In most cases, a 1 pass overwrite clears the file, and a 3 pass overwrite sanitizes the file. There is much debate on this issue, with some recommending 7 to 9 passes for the complete removal of any file's data.

After you finish using programs or performing copy/paste operations in Windows, all kinds of data can be left behind in the system's memory. Other programs and other users can obtain this data.

Internet Explorer can store a record of almost everything that you type into any web site form. Form data can be things such as all the keywords you have ever typed into a search engine and personal information such as your name and address and passwords.

Common Dialogs are the standard Windows file open/save boxes that most programs use to open and save files. Some versions of Windows maintain hidden history lists for these boxes.

When a web page is requested and delivered to your browser, the images and documents associated with the web page are saved in a temporary Internet file or cache so that the next time they are requested; they are accessed from your computer and not over the web (unless a change has occurred).

A file with "slack space" refers to the unused portion of a cluster on a hard drive that a file is stored on.

A cookie is a small message of text stored on your computer. The main purpose of cookies is to identify users and possibly prepare customized Web pages for them. When you enter a Web site using cookies, you may be asked to fill out a form providing such information as your name and interests. This information is packaged into a cookie and sent to your Web browser, which stores it for later use. The next time you go to the same Web site, your browser will send the cookie to the Web server. The server can use this information to present you with custom Web pages. So, for example, instead of seeing just a generic welcome page you might see a welcome page with your name on it.

There are multiple Index.dat files in different directories that keep a copy of whatever there is in that folder and they continue keeping those records even after you have deleted the contents of those folders. These files can be very hard to find and erase. If you are in Windows, even with "Show hidden files and folders" enabled, these files are not visible and cannot be found if you do a search for these files. The reason that these files are so invisible is that they are not just hidden, they have been designated as "system" files. System files and folders are treated differently in DOS and Windows and are effectively cloaked from casual searches.

Third party software applications (browsers, email, graphical editors, instant messaging, chat, P2P, image viewers, etc.) record activity like pictures viewed, websites visited, media played, and last used files. A plugin is a small piece of interface software, specifically designed for each application, that allows your computer to erase this information.

Logging files keep records of URLs you have tried to access that resulted in an error.

These are special directories containing backups of the registry entries.

Most programs leave garbage in the windows registry that can be recovered. Evidence of Internet sites is one example that remains until your Windows registry is rebuilt.

Streams are history kept by Windows about your Explorer window settings.

After one of your programs crashes, or Windows experiences a glitch, errors can accumulate on your drives. One of the common minor errors to appear on most drives over a period of time, is that Windows gets confused about the amount of free space on the drive. To help fix these files, the Windows utility Scan Disk can create a lot of .CHK files at the root directory of drives. These files usually contain junk data and can be erased to help keep drives clean.

A swap file is an area on your hard disk used as virtual memory and contains data and information that has been accessed on your hard drive.

Windows creates temporary files in a folder named "Temp" that stores files used during installation of a program or files used while an application is running.