Tried to download 17 updates and all 17 downloads failed all it tells me is error 646

Read the solution from this forum @ http://forums.techarena.in/operating-systems/1088315.htm

Hope it will solve your problem.

The error code 646 will appear when any of the Microsoft office application updates fail to install. Run fixit provided in the below link and then try to install updates.
http://support.microsoft.com/kb/971058

What error code?

http://www.vistaheads.com/forums/microsoft-public-windowsupdate/322548-error-646-a.html read that page, has all the info you need on how to get info and the official MS page to fix it.
Should be able to help you properly

sounds like your internet connection is compromised. From Compaq's error code management page. see here for details

Alright here is what you do.

Go to support.microsoft.com and type the name of the updates that are failing.

Once you download them on your computer, Right click on them, and Run as Administrator. This way, you will not get any errors.
Do let me know if that worked, otherwise, we can find something else.

Apparently, your Windows failed to UPDATE properly. Microsoft distributes updates on "Update Tuesday" - second Tuesday of the month.
Go to the update page to complete the updates:
http://www.update.microsoft.com

Sometimes MS update has compatibility issue.Better no to install cause sometimes it can create a bug (Blue Screen Crash) to your system.Try to restore yor windows 7 to an earlier point and the error message gone.Also try to turn off your automatic update so that you can choose your update to be installed.

You need to disable your firewall. If you’re using McAfee Personal Firewall, or Norton Internet Security or another Firewall vendor, see vendor support page for assistance in disabling it (temporarily).

If you’re using the built-in Vista Firewall, keep reading.

- Open the Control Panel and select Security.

-Select Turn Windows Firewall on or off.

- Select Off (not recommended), click Apply and then OK.

- Back at the Windows Update screen, click the Try again button.

-The download(s) and installation should start…

-And this time successfully install. Now make sure to re-enable your Firewall once your PC restarts.

* Though this solution will work for most Vista Update errors.

That fatal error warning message is not coming from your operating system - it is coming from a virus. Do not follow whatever instructions boxes like that may tell you until after the following process.

Turn on your machine's firewall and tick NO EXCEPTIONS. Download an anti-virus product like AVG from download.com. Install it, update it until it says it has all updates, and then do a complete scan of your machine removing viruses.

Reboot.

Navigate to WINDOWS UPDATE on your start bar and allow it to install all updates it can, even optional ones.

Reboot.

Go to ADD REMOVE PROGRAMS from CONTROL PANEL and remove all security software besides the anti-virus you just installed, since this software has failed and is now unreliable.

Good luck...