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How to scan your computer with CCleaner

CCleaner scans temporary folders and the registry for unwanted items. It can also prevent unwanted programs from running when Windows starts up.

Before You Begin

CCleaner is a malware-removal tool that cleans web browser temporary folders and files, cleans the Windows registry of unwanted or unused registry keys, and provides an easy way of preventing unwanted programs from running at startup.

There are several steps you should take when cleaning an infected computer. Before running CCleaner, we recommend you review all the steps involved. Refer to 1550: How to scan and clean an infected computer.

Download and Install CCleaner

To download and install CCleaner, do the following:

  1. Download CCleaner and install it.
  2. During the installation, you will be given several install options. We recommend removing the check mark next to Add 'Run CCleaner' option to Recycle Bin context menu and Add 'Open CCleaner...' option to Recycle Bin context menu.
  3. You may be prompted to download/install the Google Chrome browser and set it as your default browser.  You can choose to allow this or not.
  4. Complete the installation.

When CCleaner finishes installing, you will have the option to open the program and view the notes.  Leave check marks in whatever boxes you want and choose finish.  The first time you open CCleaner, you may receive a prompt asking if you want to allow CCleaner to keep cookies from trusted sites such as Google, Yahoo, etc.  You can select Yes (Recommended) or No.

Scan Your Computer with CCleaner

Use CCleaner to scan your computer. It will find and remove temporary internet files, including any malware in those locations, on your system.

You should complete each of these steps:

  • Step 1 - Modify advanced settings
  • Step 2 - Scan temporary files
  • Step 3 - Scan the registry
  • Step 4 - Prevent unwanted programs from running at startup
  • Step 5 - Restart your computer

Each of these steps is detailed below.

To open CCleaner, click Start > Programs > CCleaner > CCleaner.  There may also be an icon on the desktop.

Step 1 - Modify Advanced Settings

Before you begin scanning your computer with CCleaner, you should make the following change:

  1. Click Options on the left side of the CCleaner window.
  2. Click Advanced.
  3. Remove the check mark next to Only delete files in Windows Temp folders older than 24 hours.

Step 2 - Scan Temporary Files

To scan your computer's temporary folders for unwanted files, do the following:

  1. Click Cleaner on the left side of the CCleaner window.
  2. Click the Run Cleaner button.
  3. Click OK when you are asked, This process will permanently delete files from your system. Are you sure you wish to proceed?
  4. After the scan completes, the progress bar will say 100% and a summary is displayed, including a list of files that were removed and the amount in MegaBytes (MB) that were deleted.

Step 3 - Scan the Registry

To scan your computer's registry for unwanted items, do the following:

  1. Click Registry on the left side of the CCleaner window.
  2. Click the Scan for Issues button.
  3. When the scan completes, click the Fix selected issues… button.
  4. Click Yes when you are asked, Do you want to backup changes to the registry?
  5. Browse to the folder where you would like to store the registry backup. Then click Save.
  6. CCleaner displays each issue to be fixed.
    • If you want to fix all issues identified by CCleaner, click the Fix All Selected Issues button.
    • If you want to see what changes will be made by CCleaner, you can fix each issue one by one. Click the >> button to review each issue. Click the Fix Issue button to take the action shown next to Solution: in the window.

Step 4 - Prevent Unwanted Programs From Running at Startup

To prevent unwanted programs from running when Windows starts, do the following:

  1. Click Tools on the left side of the CCleaner window.
  2. Click the Startup button.
    • This displays a list of programs that automatically run when Windows starts up.
  3. CCleaner allows you to disable or delete startup programs.
    • Look through the list of startup programs for anything that looks like malware. Click Disable on those items to prevent them from running at startup.
    • Selecting Disable does not always prevent a program from starting when Windows starts. If you find that a program is still running at startup after using CCleaner to disable it, run CCleaner again and delete the startup item.
    • Do not disable or delete the entries for software that you want to run when Windows starts. For example, you may not want to delete the startup items for Sidebar (Windows 7/Vista), AIM, Yahoo Instant Messenger, etc.
    • It's important to understand that by choosing Delete, you are only deleting the startup item, not the application. For example, if you select and delete Yahoo Instant Messenger, you are not actually deleting the Yahoo Instant Messenger application. You are only deleting the startup item that makes Yahoo Instant Messenger run when Windows starts.

Step 5 - Restart Your Computer

After running CCleaner, restart your computer.  This will ensure any programs you've prevented from starting up, will not be starting.