The hourglass displays when the system is searching for something, be that a website, or other data necessary to operate the application that is running. The 'freeze' could be caused by any number of things, but most likely lack of RAM if one is running the bare minimum for their particular windows operating system.
Another possibility could be that your 'cache' needs to be dumped. Too many cookies in there will definitely slow things down on most any machine.
Also check your windows temp (C: Windows/temp) and delete anything there with the extension "tmp". These files are supposed to be dumped when exiting your browser, but somehow they get missed most of the time.
This happens when the computer is loading and its telling you to wait and not do anything, its busy with whats going on at the moment. Just let it load.
An hourglass symbol
The mouse pointer, or cursor, changes shape.
paintbrush
two heanded arrow
hold ALT and press F4
mouse pointer
Mini Toolbar
It changes into a mini toolbar.
Four-Headed Arrow.
crosshair
Sizing Handle
the move pointer