Go into Control Panel and uninstall the Nexon Game Manager and Pando Media Booster, along with CA.
I'd recommend Revo Uninstaller Pro to do this but it's a slim chance you'll have it.
Restart your PC and try installing it again.
If you really wanna re-install Windows, the easy way would be to have a recovery partition, like from HP.
The hard part is if you clean installed your system.
I'm kind of clueless here, but try uninstalling and reinstalling those things first.
I just re-read it, You asked How to reboot Vista.
Click Start, click the arrow and click Shutdown.