you can not do an inplace upgrade from a 32 bit OS to a 64 bit one.
You need to do a backup of your files, boot with the W7 dvd and select custom install.
Further information here.
http://windows.microsoft.com/en-us/windows7/32-bit-and-64-bit-Windows-frequently-asked-questions
Hello, I am about to build my first computer and I have a question. In short, can I upgrade Vista Business 32bit to Win7 Professional 64bit without any problems? In case you were wondering
I am a student and this is the cheapest way to get Win7.
Thanks in advance.

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