Get rid of Junk Files

You will be able to answer yourself with a bit of help. If you want someone to use your product are you going to say, "You are clean and do not need us"?
Use Ccleaner and you will be fine.
In addition, if they clean more than cc does, they may touch registry and other vital components.
You can go to search and type %temp%. Those are temp files that if not used in the last few days can be deleted.

You are very welcome.
You should do this too
Disk Cleanup - Open and Use

To maintain your computer

10 Tips on How to Properly Maintain Your Computer
ignore, reg cleaners.

Steps that I did not notice on the guide include:

Running a scan disc before doing a defrag

Using Microsoft Security Essentials and Malwarebytes.

Making System Restore points, at least once a week

Makaing a system Image once a month (varies by user)

Not relying on your A/V common sense, should prevail. You know of many sites can cause a problem.

Do not use any reg cleaning or optimizing software.

Download and use Ccleaner about once every two months. Untick any registry entries.
http://www.piriform.com/

Download and use PSI, to to be sure that all of your software is up to date
http://secunia.com/vulnerability_scanning/personal/

If you follow these instructions, you will be trouble free for a long time to come.

Be sure to back up your hard drive about once a month (varies by user) and to keeep system restore points up to date.

Optimize Windows 7