Of course you cannot perform such an upgrade: those versions are architecturally different in the way the operating system code is written (for example, you need 64 bit drivers for all of your devices).
You have to verify your computer's compatibility with 64 bit Windows, locate the drivers for any device installed in your system, perform a full backup of your data and perform a new clean installation of the 64 bit version of Windows.
Bye.
Luigi Bruno - Microsoft Community Contributor 2011 Award
