There where reports that there was a problem with upgrading Vista to Windows 7, but after Microsoft investigation it turn out that this was not a problem but lack of proper preparation on end user side.

Basically you can not upgrade Vista 32 Bit version to Windows 7 64 bit version. If you purchase by mistake or wrong advise Windows 7 64 Bit upgrade for Vista 32 Bit, you should contact shop where you purchased it and replace with 32 Bit version.