virtualbox.org

Greetings, i have a problem with installing windows server 2012 r2 on my VB.
my system is : Intell Pentium i7 4700MQ (Windows 8.1 64bit)
and in the list of choosing system i can choose only 32 bit's system? how can i repair it? or where is the problem?
Thank you.

1) 64-bit guests need hardware-virtualzation enabled in the hosts bios.
2) when creating the 64-bit guest you must select 64-bit in General -> Basic -> version.
3) If running Windows as host you must make sure hyper-v or xp mode is not enabled on the host. MS does not play well and wants it all.