Recuva found different results?

Hello all! I would first like to say that I genuinely believe in CCleaner and Recuva, I'm just kinda having trouble with them at the moment, and I could use some know-how to solve some problems. Please panda bear with me.

Main Objective: Get rid of internet history and documents from more than 2 years ago.

Extra Information: This computer was used heavily for two years, then I used my browser to clear the history, and then I placed this computer in storage and it was not used for two years. Today, I first used my browser to delete my internet history, cache, cookies, saved passwords, and so on. Then, with CCleaner, I used the "Analyze" and "Clean" options to find more files to delete. I then used CCleaner's free space wipe and did 1 pass. I waited an hour and did another 1 pass because I was paranoid.

Recuva Procedure and Problems: I installed Recuva today and ran a deep scan. It showed me around 20,000 files, while 50,000 were ignored. I tried to show the ignored files by clicking on "show zero byte files, non-deleted files," and "files hidden in directories." Recuva started malfunctioning. The files were loading very quickly and eventually I believe they did all load, however, I could not change any settings any more. For example, I would click on file number 5, but then the drop down boxed forced me to only view the bottom files. Even stranger, the language switched to Vietnamese. I could not change the language. I could not even scroll to change the language. It would force me back down. I went around this by using my keys to go up to "English" and I hit enter, and it tried to load English but then it would go crazy, switching between many different languages in the drop down box before going back to Vietnamese. At this point, I could not make any more changes, so I decided to restart my computer.

The results and language were still the same after the restart, and I was getting frustrated, so I uninstalled Recuva and reinstalled it. After reinstallation, I was less successful. I ran the deep scan again and it only found 5,000 files (7,000 were ignored.) I didn't want to take the risk of trying to see the ignored files and make Recuva go crazy again, so I just overwrote the files that were already shown. When the overwriting was finished, it said that 2,700 were overwritten in 8 minutes. However, individual files in the box said that some were overwritten, while some were not!

Q's! John Q-sack would be proud!

1. What should I do next to insure that all the files (especially documents and internet history) are overwritten?

2. Why did Recuva act so strangely? Was it overloaded?