Hi kadza - Welcome to w7forums
Yep, I know how.
Use Windows 7 64-Bit media and perform a clean install. Then you can re-install all your software.
If you are wondering a clean install in required to change Bit versions. There are to many differences in the code to perform a upgrade or downgrade. However the same key will work with both 32-Bit and 64-Bit, so it is only a matter of re-install and using the same key.