My PC is under WinXP SP3
I have tested the following versions:
The first one is the latest installer from website's download menu (windows 32 bits).
The last one is currently the latest version from daily builds. And this version I have unpacked and tried to do the same and these commands don't work. So it is not because of my actions. Numpad 7 doesn't work too
This problem happens starting the default project
On (some? older?) windows computers, the numerical pad needs to be set to work, there's some numlock button on your keyboard that does this.
Apart from that... this is for sure not a Blender bug. Try it on another system to verify, this is so basic, if this fails it's something in your system that refuses to send proper events. Maybe keyboard layout stuff...