UserAssist uncovers hidden Windows activity logs
It's no secret that Windows records many details about how your PC is being used. A quick look at the Start menu will probably uncover the programs you've launched recently, and the documents you've opened, for instance, while histories in WordPad, Paint, the Run box and so on reveal even more about your recent activities.
What's not quite as well known, though, is that Windows also maintains a longer and separate history of all the programs launched on your computer, including details like the number of times they've been run, and the last execution date and time. This information is stored in the Registry (HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\UserAssist), but it's encrypted, so you'll need something like the free UserAssist tool to find out more (for Windows 7 use this version --for Windows XP or Vista go here).
The program is easy to use, no need to install anything, just run it and you'll see a table with all the software you've been running recently. This can go far beyond the usual "last 10 documents" in a typical "most recently used" list; you may have as many as a thousand applications listed. Windows records a last used date, too, so if you click the "Last" column header then you can view exactly what's been used on your PC, in order, extending back for quite some time.
This has obvious applications if you'd like to know more about what's happening on a particular system. What are your kids really doing on their PC, say? How is an employee spending their day on a work computer? UserAssist may offer useful clues.
The program isn't just about checking up on people, though. If a friend reports that his or her PC is unstable and crashing regularly, for instance, then it could be very useful to see exactly what's going on before things go horribly wrong. There's no way they're going to remember every detail, but running UserAssist might tell you what you need to know. (And if it doesn't do so immediately, you can at least save the list as a text or HTML report for easy analysis later.)
If you're more concerned about the privacy implications of all this, though, the activity database may be removed in several different ways.
Install a system cleanup tool like CCleaner, say, and it's able to delete the UserAssist keys every time it runs (click Cleaner, then the Windows tab, scroll down to Advanced and make sure "User Assist History" is checked).
UserAssist can also delete the activity list on the current PC (Commands > Clear All). Or for the most effective solution, click Commands > Logging Disabled, and reboot immediately: Windows should then stop recording any UserAssist activity details at all.