How to switch from 64 bit to 32 bit windows 7

32 bit and 64 bit are two different oses.... you dont upgrade from 32 to 64 or downgrade 64 to 32... the only way is to make clean new install... i had windows 7 home 32 bit and when i installed windows 7 professional 64 bit it saved all my files on the c drive to a folder called windows.old... so you wont have to worry so much about ur data... but backup the more important files just in case...