You can check the CPU model from the Windows 7/8 from the Control Panel - System or run msinfo32. Once you have the processor model, you can check the Intel ARK site https://ark.intel.com
I just recalled that some 2008 Intel Core 2 Duo CPUs don't have VT-x and possibly some older Atom CPUs. But pretty much anything from 2010 onwards would have VT-x.
This is a link to the E7200 CPU and you can see that the Intel VT-x is indicated as "No".
As to enabling VT-x in the BIOS of the computer, it depends on the manufacturer. If I am not mistaken, Dell uses F12 to enter the BIOS. Others use F2. The menu will also vary. So it is best to consult a manufacturer manual.