I have an Esprimo Mobile V5505 with a T7300 Core2 Duo CPU and the last version of bios available for download A1D .
I found a great article http://www.linuxformat.gr/?q=content/how-unlock-and-enable-hardware-accelerated-virtualization-technology-vt-sony-vaio-laptop-and
which helped me to enable VT on my laptop .
Following the steps described in the article i found that de resource who activates VT in bios is 0x27c .
In order to activate VT :
1) Make a bootable flash as described in article and copy symcmos on it
2) Boot from flash and execute symcmos -L which will output file literal.txt on your flash
3) Modify literal.txt - the line (027C)  to (027C)  and save
4) Boot from flash again and execute symcmos -V2 -uLITERAL.TXT
5) Power off your laptop
6) Power on your laptop and check if VT is enabled - on my laptop it worked
With this solution it won't be activated any supplementary option in bios , it will enable VT only .