my install fails because 'reboot' is needed

I want to install "Sql Server Management Studio" so I can manage a remove database from my PC.

The installation first checks some rules, and one of them fails.

I clicked 'details" on the error message and got:

RebootRequiredCheck</td>
Checks if a pending computer restart is required. A pending restart can cause Setup to fail.</td>
Failed</td>
A computer restart is required. You must restart this computer before installing SQL Server.</td>

Restarting the computer manually does not help though.  (My windows version is 8.1).

Help!