You're off topic for this forum, which is dedicated to Windows Live OneCare.
However, the answer is, no. The PC you purchased came with a preinstalled OS supplied and supported by the OEM - the PC manufacturer. If they offer an x64 copy of Vista, you can obtain it from them. Otherwise, to reinstall the OS (there is no upgrade from 32 bit to 64 bit) requires a new license of Vista, although you can use an upgrade version instead of a full version.
-steve