Are all the software different for Windows 7 64 bit?

i have 4 GB of RAM n use Windows 7 32 bit.............it shows only 3.2gb usable so i want to upgrade it to 64 bit.........but my main problem is all the softwares like auto CAD 2008 Nero 8 Office 2007 which i used on 32 bit OS will not work on 64 bit.........i have to pruchase all of them which would prove much costly also all the games like COD 6 GTA Episodes from Loberty Stories Crysis Prototype ...............i wouldnt work on 64 bit .......plz help........will all these apllications work on 64 bit OS...........m very worried