Win 7 64 bit [installation issue]

HEY ALL !!  

So i have a hp laptop dv6 , intel i5 ,6 GB ram, 750 GB HD ,,runing a win7 32 bit...i installed it from a dvd that i have, name of the DVD : "Windows 7 SP1 AIO 5in1 x64 /x86" ... so it has 32 and 64 bit preactivated.

and now i want to install the 64 bit win7 from the same dvd .. but in the installation menu ,it's only shows the x86 versions of win7 .. so i can't chose the 64 bit version !!!

why is that ?! and how to install the 64 bit ??

my HD partition :

C:\ 200 GB "win7 32 bit on it"
D:\ 500 GB


thanks a lot for your time ,,and sorry about my english