Manually Editing the Registry
1. Log in as a system administrator. You will need write privileges to the system registry, and you will not have them as a 'limited' or 'normal' user.
2. Click 'Start,' 'Run,' type 'regedit' and then click 'OK.' The registry editor window should appear. If you are given an error message saying you do not have sufficient privileges to edit the registry keys, you are not logged in as an administrator.

3. Go to the File menu and select 'Backup' or 'Export' (depending on your version of Windows). The 'Save' dialog window will appear. Enter a name for the registry backup and click 'OK.'
4. Browse through the many registry hives in the column on the left looking for keys that either contain incorrect information (a mistoggled setting, etc.) or should not be there.
5. Edit the key appropriately using the panel on the right or delete the key from the left window using the Delete key or by right clicking and selecting 'Remove key.'
6. Close the registry editor when you are finished editing the registry and restart the computer. If the computer will not start up or is no longer working properly, boot into 'Safe Mode' and restore the previous registry from your backup using the registry editor.
Using a Registry Cleaner
7. Download a registry-cleaner utility. Two popular registry-cleaning software suites are CCleaner and Advanced SystemCare. Both of these applications are available for download free of charge (see Resource links).
8. Perform a virus scan on the downloaded files and install the software. You will probably need to be logged in as an administrator in order to install and use the software, since you will require write access to a vital system component (the registry).
9. Launch the utility and follow the on-screen prompts to perform a 'quick' or 'in-depth' registry scan. It's usually best to perform an in-depth scan every time, since it will usually catch more errors and does not take significantly longer than the quick scan. If the software doesn't automatically prompt you to back up your registry, do it manually.
10. Look briefly through the list of errors generated by the registry scan and choose (with a check mark) the errors you wish to remove. Sometimes the scan will generate a false positive of an error that really isn't an error. You can tell the software to ignore this instance during future scans.
11. Click the 'fix' or 'clean' button (depending on the software you use), and the software will automatically remove or properly edit the checked entries. Restart your computer. If the software fixed numerous errors, you may notice your system starts up much more quickly.