How to turn on Intel VT in MacBook Pro 2011 (MC721LL/A)?

Question

I used to turn on virtualization on my PC by turning it on from BIOS. But how I do it on MacBook Pro, as I am using WinXP on VMware Fusion 4.0, but its very slow, and both Windows XP and Mac OS starts lagging.

Is there any way I can turn on virtualization for Mac so that the lagging stops? It's really driving me crazy.

[Note: it's a 2.0 GHz Intel Core i7 quad-core processor ("Sandy Bridge") with 6 MB shared L3 cache for excellent multitasking.]