Not executing commands immediately For example, I press left click on the 3D view to change my cursor position. Nothing happens until I do something else, for example zooming in/out.

Also, I press 'T' to hide the tools panel. It just does it after doing something else.

In summary, whatever I do, it gets executed/showed up with "one instruction of delay".

SORY if it's a noob question

Update:
I tried Blender 2.7 and Blender 2.79.
Both on Windows 7 64 bits

Resolved :)
Now the behaviour is correct, with these Window Drawing Method configs:
Window Draw Method: Full
MultiSample: 2
Region Overlap checkd
Its normally a problem with the graphic. Check that your graphics drivers are up to date. Also once you have done and if the problem is still there mess with the windows draw settings in user preferences. The settings under system. 

Also have a look at these links
https://www.blender.org/forum/viewtopic.php?t=26691
https://www.blender.org/forum/viewtopic.php?t=28035