Can I force full speed to the indexing service of Windows?

There is a setting in the group policy for the computer, so you don't have to manually edit the registry.

• Open run dialog: Win+R
• Type "gpedit.msc" and select OK
• Browse to Computer Configuration\Administrative Templates\Windows Components\Search
• Select "Disable indexer backoff", and set it to Enabled.

This setting will not take effect until the service is restarted. The easiest way is to just reboot your computer, but you can do it live

• Open run dialog: Win+R
• Type "services.msc" and select OK
• Scroll to "Windows Search"
• Right click and select "Restart"

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See also

Summary from this page

• limit what folders are indexed
• update your Windows Search to version 4.0 (But only if Windows Updater hasn't already done)
• HKLM\Software\Policies\Microsoft\Windows\Windows Search\Gathering Manager\DisableBackoff
  set the value to 1 if you are on a non-domain joined computer

• on domain joined computer, edit your group policy and set Disable indexer backoff to enabled Computer Configuration\Administrative Templates\Windows Components\Search

  DisableBackoff=1 in other words: Don't worry about system activity - just index and get it over with already!

Above registry "hack" in the first top rated answer only seems to apply to Windows search 4 in XP, not 7.

The correct path to the registry key is:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Search\Gathering Manager

Furthermore, you have to change the permissions to allow the change, then restart the search service.

These are the instructions I found which worked:

1. Start up the registry editor. Press Windows Logo Key+R, type in regedit, and press enter. Alternatively, if you don’t have a Windows Logo Key on your keyboard, click the start menu button, type in run, press enter, then type in regedit, and press enter once more.

2. Find the key to change. In the folder view tree to the left, browse your way through to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Search\Gathering Manager. Once you’re there (the Gathering Manager folder is selected in the tree), a whole bunch of keys will appear in the right-hand window. Find the one that’s called DisableBackOffOnUser.

   • This key is what it’s all about. It basically determines whether or not the indexing process should stop when the user’s doing something. There are other similar keys that you could edit to force the indexer to keep indexing even if you were playing Bioshock while ripping a DVD and little flames were coming from your processor, but that’s not really necessary, so we’ll just focus on this one key. Unfortunately, Vista won’t let you change the key’s value (if you try, it’ll let you down with: Error writing the value’s new contents.), even though we've been elevated to have administrator privileges. So, to get permission to change the key's value, you need to do the following.
     
     

3. Click on the key, so that it’s selected. Go to the Edit menu and select Permissions. In the pop-up window, click the Advanced button. In the new pop-up window, select the Owner tab, then in the list below Change owner to:, select Administrators, then click the OK button on both pop-up windows to return to the registry editor.

4. Now, we can double-click the key and change its value to 1 (one). Click OK and close the registry editor.

5. Restart your computer (or just restart the Windows Search service if you know how), and the indexer will start indexing your stuff even while you’re working. In the about twenty minutes it took me to write this, Vista has indexed 46,000 files on my computer.