Microsoft introduced a new feature called SuperFetch in Windows Vista. You can read my post about SuperFetch by clicking here.
Most modern computers have a lot of RAM available for the operating system. Vista's SuperFetch feature just makes good use of this RAM to speed things up. Your memory is filled with applications that you are more likely to use by SuperFetch. That is the reason why you see such high RAM usages in your task manager.
To conclude Vista uses all your memory to decrease system response time. You should not be complaining about Vista. Just complain why previous versions of Windows did not make good use of your RAM!
You can read a more detailed explanation here.
