Bonjour handles Home Sharing, the remote app, and syncing to Apple TVs. If you're doing any of that, it's best not to uninstall Bonjour.
Uninstalling and then reinstalling iTunes should also reinstall Bonjour.
For the reinstall, use an installer downloaded from the Apple website:
http://www.apple.com/itunes/download/
... or you could get it back via your Apple Software Update for Windows.
If you'd prefer not to uninstall iTunes, try the following procedure.
Download and save a copy of the iTunesSetup.exe (or iTunes64setup.exe) installer file to your hard drive:
http://www.apple.com/itunes/download/
Download and install the free trial version of WinRAR:
http://www.rarlab.com/
Right-click the iTunesSetup.exe (or iTunes64setup.exe), and select "Extract to iTunesSetup" (or "Extract to iTunes64Setup"). WinRAR will expand the contents of the file into a folder called "iTunesSetup" (or "iTunes64Setup").
Go into the folder and doubleclick the Bonjour.msi (or Bonjour64.msi) to do a standalone Bonjour install.